Explicitly export content providers

In a future version of Android, the default value for
<provider android:exported> will change from true to false.
Explicitly set android:exported="true"

Bug: 3306452
Change-Id: I3d3e3564aa6a0fc8ba049d043612e94c67f1ec70
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index c812fb6..790b39c 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -14,7 +14,7 @@
     <application android:process="android.process.media"
                  android:label="@string/app_label">
         <provider android:name="MediaProvider" android:authorities="media"
-                android:multiprocess="false">
+                android:multiprocess="false" android:exported="true">
             <grant-uri-permission android:pathPrefix="/external/" />
             <path-permission
                     android:pathPrefix="/external/"