Source/WebCore/loader/DocumentThreadableLoader.cpp - platform/external/webkit - Git at Google

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following disclaimer
  * in the documentation and/or other materials provided with the
  * distribution.
  *     * Neither the name of Google Inc. nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "DocumentThreadableLoader.h"

 #include "AuthenticationChallenge.h"
 #include "CrossOriginAccessControl.h"
 #include "CrossOriginPreflightResultCache.h"
 #include "Document.h"
 #include "DocumentThreadableLoaderClient.h"
 #include "Frame.h"
 #include "FrameLoader.h"
 #include "ResourceHandle.h"
 #include "ResourceLoadScheduler.h"
 #include "ResourceRequest.h"
 #include "SecurityOrigin.h"
 #include "SubresourceLoader.h"
 #include "ThreadableLoaderClient.h"
 #include <wtf/UnusedParam.h>

 namespace WebCore {

 void DocumentThreadableLoader::loadResourceSynchronously(Document* document, const ResourceRequest& request, ThreadableLoaderClient& client, const ThreadableLoaderOptions& options)
 {
     // The loader will be deleted as soon as this function exits.
     RefPtr<DocumentThreadableLoader> loader = adoptRef(new DocumentThreadableLoader(document, &client, LoadSynchronously, request, options, String()));
     ASSERT(loader->hasOneRef());
 }

 PassRefPtr<DocumentThreadableLoader> DocumentThreadableLoader::create(Document* document, ThreadableLoaderClient* client, const ResourceRequest& request, const ThreadableLoaderOptions& options, const String& optionalOutgoingReferrer)
 {
     RefPtr<DocumentThreadableLoader> loader = adoptRef(new DocumentThreadableLoader(document, client, LoadAsynchronously, request, options, optionalOutgoingReferrer));
     if (!loader->m_loader)
         loader = 0;
     return loader.release();
 }

 DocumentThreadableLoader::DocumentThreadableLoader(Document* document, ThreadableLoaderClient* client, BlockingBehavior blockingBehavior, const ResourceRequest& request, const ThreadableLoaderOptions& options, const String& optionalOutgoingReferrer)
     : m_client(client)
     , m_document(document)
     , m_options(options)
     , m_optionalOutgoingReferrer(optionalOutgoingReferrer)
     , m_sameOriginRequest(document->securityOrigin()->canRequest(request.url()))
     , m_async(blockingBehavior == LoadAsynchronously)
 {
     ASSERT(document);
     ASSERT(client);
     // Setting an outgoing referer is only supported in the async code path.
     ASSERT(m_async || m_optionalOutgoingReferrer.isEmpty());

     if (m_sameOriginRequest || m_options.crossOriginRequestPolicy == AllowCrossOriginRequests) {
         loadRequest(request, DoSecurityCheck);
         return;
     }

     if (m_options.crossOriginRequestPolicy == DenyCrossOriginRequests) {
         m_client->didFail(ResourceError(errorDomainWebKitInternal, 0, request.url().string(), "Cross origin requests are not supported."));
         return;
     }

     ASSERT(m_options.crossOriginRequestPolicy == UseAccessControl);

     OwnPtr<ResourceRequest> crossOriginRequest = adoptPtr(new ResourceRequest(request));
     crossOriginRequest->removeCredentials();
     crossOriginRequest->setAllowCookies(m_options.allowCredentials);

     if (!m_options.forcePreflight && isSimpleCrossOriginAccessRequest(crossOriginRequest->httpMethod(), crossOriginRequest->httpHeaderFields()))
         makeSimpleCrossOriginAccessRequest(*crossOriginRequest);
     else {
         m_actualRequest = crossOriginRequest.release();

         if (CrossOriginPreflightResultCache::shared().canSkipPreflight(document->securityOrigin()->toString(), m_actualRequest->url(), m_options.allowCredentials, m_actualRequest->httpMethod(), m_actualRequest->httpHeaderFields()))
             preflightSuccess();
         else
             makeCrossOriginAccessRequestWithPreflight(*m_actualRequest);
     }
 }

 void DocumentThreadableLoader::makeSimpleCrossOriginAccessRequest(const ResourceRequest& request)
 {
     ASSERT(isSimpleCrossOriginAccessRequest(request.httpMethod(), request.httpHeaderFields()));

     // Cross-origin requests are only defined for HTTP. We would catch this when checking response headers later, but there is no reason to send a request that's guaranteed to be denied.
     if (!request.url().protocolInHTTPFamily()) {
         m_client->didFail(ResourceError(errorDomainWebKitInternal, 0, request.url().string(), "Cross origin requests are only supported for HTTP."));
         return;
     }

     // Make a copy of the passed request so that we can modify some details.
     ResourceRequest crossOriginRequest(request);
     crossOriginRequest.setHTTPOrigin(m_document->securityOrigin()->toString());

     loadRequest(crossOriginRequest, DoSecurityCheck);
 }

 void DocumentThreadableLoader::makeCrossOriginAccessRequestWithPreflight(const ResourceRequest& request)
 {
     ResourceRequest preflightRequest(request.url());
     preflightRequest.removeCredentials();
     preflightRequest.setHTTPOrigin(m_document->securityOrigin()->toString());
     preflightRequest.setAllowCookies(m_options.allowCredentials);
     preflightRequest.setHTTPMethod("OPTIONS");
     preflightRequest.setHTTPHeaderField("Access-Control-Request-Method", request.httpMethod());

     const HTTPHeaderMap& requestHeaderFields = request.httpHeaderFields();

     if (requestHeaderFields.size() > 0) {
         Vector<UChar> headerBuffer;
         HTTPHeaderMap::const_iterator it = requestHeaderFields.begin();
         append(headerBuffer, it->first);
         ++it;

         HTTPHeaderMap::const_iterator end = requestHeaderFields.end();
         for (; it != end; ++it) {
             headerBuffer.append(',');
             headerBuffer.append(' ');
             append(headerBuffer, it->first);
         }

         preflightRequest.setHTTPHeaderField("Access-Control-Request-Headers", String::adopt(headerBuffer));
     }

     preflightRequest.setPriority(request.priority());

     loadRequest(preflightRequest, DoSecurityCheck);
 }

 DocumentThreadableLoader::~DocumentThreadableLoader()
 {
     if (m_loader)
         m_loader->clearClient();
 }

 void DocumentThreadableLoader::cancel()
 {
     if (!m_loader)
         return;

     m_loader->cancel();
     m_loader->clearClient();
     m_loader = 0;
     m_client = 0;
 }

 void DocumentThreadableLoader::setDefersLoading(bool value)
 {
     if (m_loader)
         m_loader->setDefersLoading(value);
 }

 void DocumentThreadableLoader::willSendRequest(SubresourceLoader* loader, ResourceRequest& request, const ResourceResponse& redirectResponse)
 {
     ASSERT(m_client);
     ASSERT_UNUSED(loader, loader == m_loader);

     if (!isAllowedRedirect(request.url())) {
         RefPtr<DocumentThreadableLoader> protect(this);
         m_client->didFailRedirectCheck();
         request = ResourceRequest();
     } else {
         if (m_client->isDocumentThreadableLoaderClient())
             static_cast<DocumentThreadableLoaderClient*>(m_client)->willSendRequest(request, redirectResponse);
     }
 }

 void DocumentThreadableLoader::didSendData(SubresourceLoader* loader, unsigned long long bytesSent, unsigned long long totalBytesToBeSent)
 {
     ASSERT(m_client);
     ASSERT_UNUSED(loader, loader == m_loader);

     m_client->didSendData(bytesSent, totalBytesToBeSent);
 }

 void DocumentThreadableLoader::didReceiveResponse(SubresourceLoader* loader, const ResourceResponse& response)
 {
     ASSERT(m_client);
     ASSERT_UNUSED(loader, loader == m_loader);

     String accessControlErrorDescription;
     if (m_actualRequest) {
         if (!passesAccessControlCheck(response, m_options.allowCredentials, m_document->securityOrigin(), accessControlErrorDescription)) {
             preflightFailure(response.url(), accessControlErrorDescription);
             return;
         }

         OwnPtr<CrossOriginPreflightResultCacheItem> preflightResult = adoptPtr(new CrossOriginPreflightResultCacheItem(m_options.allowCredentials));
         if (!preflightResult->parse(response, accessControlErrorDescription)
             || !preflightResult->allowsCrossOriginMethod(m_actualRequest->httpMethod(), accessControlErrorDescription)
             || !preflightResult->allowsCrossOriginHeaders(m_actualRequest->httpHeaderFields(), accessControlErrorDescription)) {
             preflightFailure(response.url(), accessControlErrorDescription);
             return;
         }

         CrossOriginPreflightResultCache::shared().appendEntry(m_document->securityOrigin()->toString(), m_actualRequest->url(), preflightResult.release());
     } else {
         if (!m_sameOriginRequest && m_options.crossOriginRequestPolicy == UseAccessControl) {
             if (!passesAccessControlCheck(response, m_options.allowCredentials, m_document->securityOrigin(), accessControlErrorDescription)) {
                 m_client->didFail(ResourceError(errorDomainWebKitInternal, 0, response.url().string(), accessControlErrorDescription));
                 return;
             }
         }

         m_client->didReceiveResponse(response);
     }
 }

 void DocumentThreadableLoader::didReceiveData(SubresourceLoader* loader, const char* data, int dataLength)
 {
     ASSERT(m_client);
     ASSERT_UNUSED(loader, loader == m_loader);

     // Preflight data should be invisible to clients.
     if (m_actualRequest)
         return;

     m_client->didReceiveData(data, dataLength);
 }

 void DocumentThreadableLoader::didReceiveCachedMetadata(SubresourceLoader* loader, const char* data, int dataLength)
 {
     ASSERT(m_client);
     ASSERT_UNUSED(loader, loader == m_loader);

     // Preflight data should be invisible to clients.
     if (m_actualRequest)
         return;

     m_client->didReceiveCachedMetadata(data, dataLength);
 }

 void DocumentThreadableLoader::didFinishLoading(SubresourceLoader* loader, double finishTime)
 {
     ASSERT(loader == m_loader);
     ASSERT(m_client);
     didFinishLoading(loader->identifier(), finishTime);
 }

 void DocumentThreadableLoader::didFinishLoading(unsigned long identifier, double finishTime)
 {
     if (m_actualRequest) {
         ASSERT(!m_sameOriginRequest);
         ASSERT(m_options.crossOriginRequestPolicy == UseAccessControl);
         preflightSuccess();
     } else
         m_client->didFinishLoading(identifier, finishTime);
 }

 void DocumentThreadableLoader::didFail(SubresourceLoader* loader, const ResourceError& error)
 {
     ASSERT(m_client);
     // m_loader may be null if we arrive here via SubresourceLoader::create in the ctor
     ASSERT_UNUSED(loader, loader == m_loader || !m_loader);

     m_client->didFail(error);
 }

 bool DocumentThreadableLoader::getShouldUseCredentialStorage(SubresourceLoader* loader, bool& shouldUseCredentialStorage)
 {
     ASSERT_UNUSED(loader, loader == m_loader || !m_loader);

     if (!m_options.allowCredentials) {
         shouldUseCredentialStorage = false;
         return true;
     }

     return false; // Only FrameLoaderClient can ultimately permit credential use.
 }

 void DocumentThreadableLoader::didReceiveAuthenticationChallenge(SubresourceLoader* loader, const AuthenticationChallenge& challenge)
 {
     ASSERT(loader == m_loader);
     // Users are not prompted for credentials for cross-origin requests.
     if (!m_sameOriginRequest) {
 #if PLATFORM(MAC) || USE(CFNETWORK) || USE(CURL)
         loader->handle()->receivedRequestToContinueWithoutCredential(challenge);
 #else
         // These platforms don't provide a way to continue without credentials, cancel the load altogether.
         UNUSED_PARAM(challenge);
         RefPtr<DocumentThreadableLoader> protect(this);
         m_client->didFail(loader->blockedError());
         cancel();
 #endif
     }
 }

 void DocumentThreadableLoader::receivedCancellation(SubresourceLoader* loader, const AuthenticationChallenge& challenge)
 {
     ASSERT(m_client);
     ASSERT_UNUSED(loader, loader == m_loader);
     m_client->didReceiveAuthenticationCancellation(challenge.failureResponse());
 }

 void DocumentThreadableLoader::preflightSuccess()
 {
     OwnPtr<ResourceRequest> actualRequest;
     actualRequest.swap(m_actualRequest);

     actualRequest->setHTTPOrigin(m_document->securityOrigin()->toString());

     // It should be ok to skip the security check since we already asked about the preflight request.
     loadRequest(*actualRequest, SkipSecurityCheck);
 }

 void DocumentThreadableLoader::preflightFailure(const String& url, const String& errorDescription)
 {
     m_actualRequest = 0; // Prevent didFinishLoading() from bypassing access check.
     m_client->didFail(ResourceError(errorDomainWebKitInternal, 0, url, errorDescription));
 }

 void DocumentThreadableLoader::loadRequest(const ResourceRequest& request, SecurityCheckPolicy securityCheck)
 {
     // Any credential should have been removed from the cross-site requests.
     const KURL& requestURL = request.url();
     ASSERT(m_sameOriginRequest || requestURL.user().isEmpty());
     ASSERT(m_sameOriginRequest || requestURL.pass().isEmpty());

     if (m_async) {
         // Don't sniff content or send load callbacks for the preflight request.
         bool sendLoadCallbacks = m_options.sendLoadCallbacks && !m_actualRequest;
         bool sniffContent = m_options.sniffContent && !m_actualRequest;
         // Keep buffering the data for the preflight request.
         bool shouldBufferData = m_options.shouldBufferData || m_actualRequest;

         // Clear the loader so that any callbacks from SubresourceLoader::create will not have the old loader.
         m_loader = 0;
         m_loader = resourceLoadScheduler()->scheduleSubresourceLoad(m_document->frame(), this, request, ResourceLoadPriorityMedium, securityCheck, sendLoadCallbacks,
                                                                     sniffContent, m_optionalOutgoingReferrer, shouldBufferData);
         return;
     }

     // FIXME: ThreadableLoaderOptions.sniffContent is not supported for synchronous requests.
     StoredCredentials storedCredentials = m_options.allowCredentials ? AllowStoredCredentials : DoNotAllowStoredCredentials;

     Vector<char> data;
     ResourceError error;
     ResourceResponse response;
     unsigned long identifier = std::numeric_limits<unsigned long>::max();
     if (m_document->frame())
         identifier = m_document->frame()->loader()->loadResourceSynchronously(request, storedCredentials, error, response, data);

     // No exception for file:/// resources, see <rdar://problem/4962298>.
     // Also, if we have an HTTP response, then it wasn't a network error in fact.
     if (!error.isNull() && !requestURL.isLocalFile() && response.httpStatusCode() <= 0) {
         m_client->didFail(error);
         return;
     }

     // FIXME: FrameLoader::loadSynchronously() does not tell us whether a redirect happened or not, so we guess by comparing the
     // request and response URLs. This isn't a perfect test though, since a server can serve a redirect to the same URL that was
     // requested. Also comparing the request and response URLs as strings will fail if the requestURL still has its credentials.
     if (requestURL != response.url() && !isAllowedRedirect(response.url())) {
         m_client->didFailRedirectCheck();
         return;
     }

     didReceiveResponse(0, response);

     const char* bytes = static_cast<const char*>(data.data());
     int len = static_cast<int>(data.size());
     didReceiveData(0, bytes, len);

     didFinishLoading(identifier, 0.0);
 }

 bool DocumentThreadableLoader::isAllowedRedirect(const KURL& url)
 {
     if (m_options.crossOriginRequestPolicy == AllowCrossOriginRequests)
         return true;

     // FIXME: We need to implement access control for each redirect. This will require some refactoring though, because the code
     // that processes redirects doesn't know about access control and expects a synchronous answer from its client about whether
     // a redirect should proceed.
     return m_sameOriginRequest && m_document->securityOrigin()->canRequest(url);
 }

 } // namespace WebCore
	/*
	* Copyright (C) 2011 Google Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met:
	*
	* * Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* * Redistributions in binary form must reproduce the above
	* copyright notice, this list of conditions and the following disclaimer
	* in the documentation and/or other materials provided with the
	* distribution.
	* * Neither the name of Google Inc. nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "DocumentThreadableLoader.h"

	#include "AuthenticationChallenge.h"
	#include "CrossOriginAccessControl.h"
	#include "CrossOriginPreflightResultCache.h"
	#include "Document.h"
	#include "DocumentThreadableLoaderClient.h"
	#include "Frame.h"
	#include "FrameLoader.h"
	#include "ResourceHandle.h"
	#include "ResourceLoadScheduler.h"
	#include "ResourceRequest.h"
	#include "SecurityOrigin.h"
	#include "SubresourceLoader.h"
	#include "ThreadableLoaderClient.h"
	#include <wtf/UnusedParam.h>

	namespace WebCore {

	void DocumentThreadableLoader::loadResourceSynchronously(Document* document, const ResourceRequest& request, ThreadableLoaderClient& client, const ThreadableLoaderOptions& options)
	{
	// The loader will be deleted as soon as this function exits.
	RefPtr<DocumentThreadableLoader> loader = adoptRef(new DocumentThreadableLoader(document, &client, LoadSynchronously, request, options, String()));
	ASSERT(loader->hasOneRef());
	}

	PassRefPtr<DocumentThreadableLoader> DocumentThreadableLoader::create(Document* document, ThreadableLoaderClient* client, const ResourceRequest& request, const ThreadableLoaderOptions& options, const String& optionalOutgoingReferrer)
	{
	RefPtr<DocumentThreadableLoader> loader = adoptRef(new DocumentThreadableLoader(document, client, LoadAsynchronously, request, options, optionalOutgoingReferrer));
	if (!loader->m_loader)
	loader = 0;
	return loader.release();
	}

	DocumentThreadableLoader::DocumentThreadableLoader(Document* document, ThreadableLoaderClient* client, BlockingBehavior blockingBehavior, const ResourceRequest& request, const ThreadableLoaderOptions& options, const String& optionalOutgoingReferrer)
	: m_client(client)
	, m_document(document)
	, m_options(options)
	, m_optionalOutgoingReferrer(optionalOutgoingReferrer)
	, m_sameOriginRequest(document->securityOrigin()->canRequest(request.url()))
	, m_async(blockingBehavior == LoadAsynchronously)
	{
	ASSERT(document);
	ASSERT(client);
	// Setting an outgoing referer is only supported in the async code path.
	ASSERT(m_async \|\| m_optionalOutgoingReferrer.isEmpty());

	if (m_sameOriginRequest \|\| m_options.crossOriginRequestPolicy == AllowCrossOriginRequests) {
	loadRequest(request, DoSecurityCheck);
	return;
	}

	if (m_options.crossOriginRequestPolicy == DenyCrossOriginRequests) {
	m_client->didFail(ResourceError(errorDomainWebKitInternal, 0, request.url().string(), "Cross origin requests are not supported."));
	return;
	}

	ASSERT(m_options.crossOriginRequestPolicy == UseAccessControl);

	OwnPtr<ResourceRequest> crossOriginRequest = adoptPtr(new ResourceRequest(request));
	crossOriginRequest->removeCredentials();
	crossOriginRequest->setAllowCookies(m_options.allowCredentials);

	if (!m_options.forcePreflight && isSimpleCrossOriginAccessRequest(crossOriginRequest->httpMethod(), crossOriginRequest->httpHeaderFields()))
	makeSimpleCrossOriginAccessRequest(*crossOriginRequest);
	else {
	m_actualRequest = crossOriginRequest.release();

	if (CrossOriginPreflightResultCache::shared().canSkipPreflight(document->securityOrigin()->toString(), m_actualRequest->url(), m_options.allowCredentials, m_actualRequest->httpMethod(), m_actualRequest->httpHeaderFields()))
	preflightSuccess();
	else
	makeCrossOriginAccessRequestWithPreflight(*m_actualRequest);
	}
	}

	void DocumentThreadableLoader::makeSimpleCrossOriginAccessRequest(const ResourceRequest& request)
	{
	ASSERT(isSimpleCrossOriginAccessRequest(request.httpMethod(), request.httpHeaderFields()));

	// Cross-origin requests are only defined for HTTP. We would catch this when checking response headers later, but there is no reason to send a request that's guaranteed to be denied.
	if (!request.url().protocolInHTTPFamily()) {
	m_client->didFail(ResourceError(errorDomainWebKitInternal, 0, request.url().string(), "Cross origin requests are only supported for HTTP."));
	return;
	}

	// Make a copy of the passed request so that we can modify some details.
	ResourceRequest crossOriginRequest(request);
	crossOriginRequest.setHTTPOrigin(m_document->securityOrigin()->toString());

	loadRequest(crossOriginRequest, DoSecurityCheck);
	}

	void DocumentThreadableLoader::makeCrossOriginAccessRequestWithPreflight(const ResourceRequest& request)
	{
	ResourceRequest preflightRequest(request.url());
	preflightRequest.removeCredentials();
	preflightRequest.setHTTPOrigin(m_document->securityOrigin()->toString());
	preflightRequest.setAllowCookies(m_options.allowCredentials);
	preflightRequest.setHTTPMethod("OPTIONS");
	preflightRequest.setHTTPHeaderField("Access-Control-Request-Method", request.httpMethod());

	const HTTPHeaderMap& requestHeaderFields = request.httpHeaderFields();

	if (requestHeaderFields.size() > 0) {
	Vector<UChar> headerBuffer;
	HTTPHeaderMap::const_iterator it = requestHeaderFields.begin();
	append(headerBuffer, it->first);
	++it;

	HTTPHeaderMap::const_iterator end = requestHeaderFields.end();
	for (; it != end; ++it) {
	headerBuffer.append(',');
	headerBuffer.append(' ');
	append(headerBuffer, it->first);
	}

	preflightRequest.setHTTPHeaderField("Access-Control-Request-Headers", String::adopt(headerBuffer));
	}

	preflightRequest.setPriority(request.priority());

	loadRequest(preflightRequest, DoSecurityCheck);
	}

	DocumentThreadableLoader::~DocumentThreadableLoader()
	{
	if (m_loader)
	m_loader->clearClient();
	}

	void DocumentThreadableLoader::cancel()
	{
	if (!m_loader)
	return;

	m_loader->cancel();
	m_loader->clearClient();
	m_loader = 0;
	m_client = 0;
	}

	void DocumentThreadableLoader::setDefersLoading(bool value)
	{
	if (m_loader)
	m_loader->setDefersLoading(value);
	}

	void DocumentThreadableLoader::willSendRequest(SubresourceLoader* loader, ResourceRequest& request, const ResourceResponse& redirectResponse)
	{
	ASSERT(m_client);
	ASSERT_UNUSED(loader, loader == m_loader);

	if (!isAllowedRedirect(request.url())) {
	RefPtr<DocumentThreadableLoader> protect(this);
	m_client->didFailRedirectCheck();
	request = ResourceRequest();
	} else {
	if (m_client->isDocumentThreadableLoaderClient())
	static_cast<DocumentThreadableLoaderClient*>(m_client)->willSendRequest(request, redirectResponse);
	}
	}

	void DocumentThreadableLoader::didSendData(SubresourceLoader* loader, unsigned long long bytesSent, unsigned long long totalBytesToBeSent)
	{
	ASSERT(m_client);
	ASSERT_UNUSED(loader, loader == m_loader);

	m_client->didSendData(bytesSent, totalBytesToBeSent);
	}

	void DocumentThreadableLoader::didReceiveResponse(SubresourceLoader* loader, const ResourceResponse& response)
	{
	ASSERT(m_client);
	ASSERT_UNUSED(loader, loader == m_loader);

	String accessControlErrorDescription;
	if (m_actualRequest) {
	if (!passesAccessControlCheck(response, m_options.allowCredentials, m_document->securityOrigin(), accessControlErrorDescription)) {
	preflightFailure(response.url(), accessControlErrorDescription);
	return;
	}

	OwnPtr<CrossOriginPreflightResultCacheItem> preflightResult = adoptPtr(new CrossOriginPreflightResultCacheItem(m_options.allowCredentials));
	if (!preflightResult->parse(response, accessControlErrorDescription)
	\|\| !preflightResult->allowsCrossOriginMethod(m_actualRequest->httpMethod(), accessControlErrorDescription)
	\|\| !preflightResult->allowsCrossOriginHeaders(m_actualRequest->httpHeaderFields(), accessControlErrorDescription)) {
	preflightFailure(response.url(), accessControlErrorDescription);
	return;
	}

	CrossOriginPreflightResultCache::shared().appendEntry(m_document->securityOrigin()->toString(), m_actualRequest->url(), preflightResult.release());
	} else {
	if (!m_sameOriginRequest && m_options.crossOriginRequestPolicy == UseAccessControl) {
	if (!passesAccessControlCheck(response, m_options.allowCredentials, m_document->securityOrigin(), accessControlErrorDescription)) {
	m_client->didFail(ResourceError(errorDomainWebKitInternal, 0, response.url().string(), accessControlErrorDescription));
	return;
	}
	}

	m_client->didReceiveResponse(response);
	}
	}

	void DocumentThreadableLoader::didReceiveData(SubresourceLoader* loader, const char* data, int dataLength)
	{
	ASSERT(m_client);
	ASSERT_UNUSED(loader, loader == m_loader);

	// Preflight data should be invisible to clients.
	if (m_actualRequest)
	return;

	m_client->didReceiveData(data, dataLength);
	}

	void DocumentThreadableLoader::didReceiveCachedMetadata(SubresourceLoader* loader, const char* data, int dataLength)
	{
	ASSERT(m_client);
	ASSERT_UNUSED(loader, loader == m_loader);

	// Preflight data should be invisible to clients.
	if (m_actualRequest)
	return;

	m_client->didReceiveCachedMetadata(data, dataLength);
	}

	void DocumentThreadableLoader::didFinishLoading(SubresourceLoader* loader, double finishTime)
	{
	ASSERT(loader == m_loader);
	ASSERT(m_client);
	didFinishLoading(loader->identifier(), finishTime);
	}

	void DocumentThreadableLoader::didFinishLoading(unsigned long identifier, double finishTime)
	{
	if (m_actualRequest) {
	ASSERT(!m_sameOriginRequest);
	ASSERT(m_options.crossOriginRequestPolicy == UseAccessControl);
	preflightSuccess();
	} else
	m_client->didFinishLoading(identifier, finishTime);
	}

	void DocumentThreadableLoader::didFail(SubresourceLoader* loader, const ResourceError& error)
	{
	ASSERT(m_client);
	// m_loader may be null if we arrive here via SubresourceLoader::create in the ctor
	ASSERT_UNUSED(loader, loader == m_loader \|\| !m_loader);

	m_client->didFail(error);
	}

	bool DocumentThreadableLoader::getShouldUseCredentialStorage(SubresourceLoader* loader, bool& shouldUseCredentialStorage)
	{
	ASSERT_UNUSED(loader, loader == m_loader \|\| !m_loader);

	if (!m_options.allowCredentials) {
	shouldUseCredentialStorage = false;
	return true;
	}

	return false; // Only FrameLoaderClient can ultimately permit credential use.
	}

	void DocumentThreadableLoader::didReceiveAuthenticationChallenge(SubresourceLoader* loader, const AuthenticationChallenge& challenge)
	{
	ASSERT(loader == m_loader);
	// Users are not prompted for credentials for cross-origin requests.
	if (!m_sameOriginRequest) {
	#if PLATFORM(MAC) \|\| USE(CFNETWORK) \|\| USE(CURL)
	loader->handle()->receivedRequestToContinueWithoutCredential(challenge);
	#else
	// These platforms don't provide a way to continue without credentials, cancel the load altogether.
	UNUSED_PARAM(challenge);
	RefPtr<DocumentThreadableLoader> protect(this);
	m_client->didFail(loader->blockedError());
	cancel();
	#endif
	}
	}

	void DocumentThreadableLoader::receivedCancellation(SubresourceLoader* loader, const AuthenticationChallenge& challenge)
	{
	ASSERT(m_client);
	ASSERT_UNUSED(loader, loader == m_loader);
	m_client->didReceiveAuthenticationCancellation(challenge.failureResponse());
	}

	void DocumentThreadableLoader::preflightSuccess()
	{
	OwnPtr<ResourceRequest> actualRequest;
	actualRequest.swap(m_actualRequest);

	actualRequest->setHTTPOrigin(m_document->securityOrigin()->toString());

	// It should be ok to skip the security check since we already asked about the preflight request.
	loadRequest(*actualRequest, SkipSecurityCheck);
	}

	void DocumentThreadableLoader::preflightFailure(const String& url, const String& errorDescription)
	{
	m_actualRequest = 0; // Prevent didFinishLoading() from bypassing access check.
	m_client->didFail(ResourceError(errorDomainWebKitInternal, 0, url, errorDescription));
	}

	void DocumentThreadableLoader::loadRequest(const ResourceRequest& request, SecurityCheckPolicy securityCheck)
	{
	// Any credential should have been removed from the cross-site requests.
	const KURL& requestURL = request.url();
	ASSERT(m_sameOriginRequest \|\| requestURL.user().isEmpty());
	ASSERT(m_sameOriginRequest \|\| requestURL.pass().isEmpty());

	if (m_async) {
	// Don't sniff content or send load callbacks for the preflight request.
	bool sendLoadCallbacks = m_options.sendLoadCallbacks && !m_actualRequest;
	bool sniffContent = m_options.sniffContent && !m_actualRequest;
	// Keep buffering the data for the preflight request.
	bool shouldBufferData = m_options.shouldBufferData \|\| m_actualRequest;

	// Clear the loader so that any callbacks from SubresourceLoader::create will not have the old loader.
	m_loader = 0;
	m_loader = resourceLoadScheduler()->scheduleSubresourceLoad(m_document->frame(), this, request, ResourceLoadPriorityMedium, securityCheck, sendLoadCallbacks,
	sniffContent, m_optionalOutgoingReferrer, shouldBufferData);
	return;
	}

	// FIXME: ThreadableLoaderOptions.sniffContent is not supported for synchronous requests.
	StoredCredentials storedCredentials = m_options.allowCredentials ? AllowStoredCredentials : DoNotAllowStoredCredentials;

	Vector<char> data;
	ResourceError error;
	ResourceResponse response;
	unsigned long identifier = std::numeric_limits<unsigned long>::max();
	if (m_document->frame())
	identifier = m_document->frame()->loader()->loadResourceSynchronously(request, storedCredentials, error, response, data);

	// No exception for file:/// resources, see <rdar://problem/4962298>.
	// Also, if we have an HTTP response, then it wasn't a network error in fact.
	if (!error.isNull() && !requestURL.isLocalFile() && response.httpStatusCode() <= 0) {
	m_client->didFail(error);
	return;
	}

	// FIXME: FrameLoader::loadSynchronously() does not tell us whether a redirect happened or not, so we guess by comparing the
	// request and response URLs. This isn't a perfect test though, since a server can serve a redirect to the same URL that was
	// requested. Also comparing the request and response URLs as strings will fail if the requestURL still has its credentials.
	if (requestURL != response.url() && !isAllowedRedirect(response.url())) {
	m_client->didFailRedirectCheck();
	return;
	}

	didReceiveResponse(0, response);

	const char* bytes = static_cast<const char*>(data.data());
	int len = static_cast<int>(data.size());
	didReceiveData(0, bytes, len);

	didFinishLoading(identifier, 0.0);
	}

	bool DocumentThreadableLoader::isAllowedRedirect(const KURL& url)
	{
	if (m_options.crossOriginRequestPolicy == AllowCrossOriginRequests)
	return true;

	// FIXME: We need to implement access control for each redirect. This will require some refactoring though, because the code
	// that processes redirects doesn't know about access control and expects a synchronous answer from its client about whether
	// a redirect should proceed.
	return m_sameOriginRequest && m_document->securityOrigin()->canRequest(url);
	}

	} // namespace WebCore