Fix AssertionFailedError in MediaSessionCompatTest

This CL sets a MediaButtonReceiver in the test app to make
MediaSessionCompat constructor not throw IllegalArgumentException.

Bug: 34035629
Test: Tested on API < 21 devices
Change-Id: I22bcbe796bc5344fefcdd0531a62f96c60f83a11
diff --git a/media-compat/tests/AndroidManifest.xml b/media-compat/tests/AndroidManifest.xml
index 00de2db..1216194 100644
--- a/media-compat/tests/AndroidManifest.xml
+++ b/media-compat/tests/AndroidManifest.xml
@@ -27,6 +27,11 @@
     <application android:supportsRtl="true">
         <uses-library android:name="android.test.runner"/>
         <activity android:name="android.support.v4.media.session.TestActivity" />
+        <receiver android:name="android.support.v4.media.session.MediaButtonReceiver" >
+            <intent-filter>
+                <action android:name="android.intent.action.MEDIA_BUTTON" />
+            </intent-filter>
+        </receiver>
     </application>
 
     <instrumentation