Add an API to expose the server's cookie domain.

Bug: http://b/3041920
Change-Id: I5c8cce92d68a74a18a8b2ea0f75f6b48ab3601d5
diff --git a/src/main/java/com/google/mockwebserver/MockWebServer.java b/src/main/java/com/google/mockwebserver/MockWebServer.java
index a938a27..ba92458 100644
--- a/src/main/java/com/google/mockwebserver/MockWebServer.java
+++ b/src/main/java/com/google/mockwebserver/MockWebServer.java
@@ -106,6 +106,16 @@
     }
 
     /**
+     * Returns a cookie domain for this server. This returns the server's
+     * non-loopback host name if it is known. Otherwise this returns ".local"
+     * for this server's loopback name.
+     */
+    public String getCookieDomain() {
+        String hostName = getHostName();
+        return hostName.contains(".") ? hostName : ".local";
+    }
+
+    /**
      * Sets the number of bytes of the POST body to keep in memory to the given
      * limit.
      */