Migrate AudioFocusChangeListener to browser and always send GAIN

media/base/android/media_player_listener.cc

Index: media/base/android/media_player_listener.cc
diff --git a/media/base/android/media_player_listener.cc b/media/base/android/media_player_listener.cc
index 861a34f7b0b3a636540b29b5ba0cf13fbd52db8a..e53f00e70e8752582ef2257c37ce78cd2cffd728 100644
--- a/media/base/android/media_player_listener.cc
+++ b/media/base/android/media_player_listener.cc
@@ -39,14 +39,7 @@ void MediaPlayerListener::CreateMediaPlayerListener(
   }
 }
 
-
 void MediaPlayerListener::ReleaseMediaPlayerListenerResources() {
-  JNIEnv* env = AttachCurrentThread();
-  CHECK(env);
-  if (!j_media_player_listener_.is_null()) {
-    Java_MediaPlayerListener_releaseResources(
-        env, j_media_player_listener_.obj());
-  }
   j_media_player_listener_.Reset();
 }