stagefright: don't use ALooperRoster mutex for reply handling

Change replyID-s from uint32_t to an object
Move reply handling into the loopers (to reuse a common mutex)

Bug: 19607784
Change-Id: Iaa035b846c424c5687ed17ce1079b325e86c54be
diff --git a/media/ndk/NdkMediaCodec.cpp b/media/ndk/NdkMediaCodec.cpp
index 46757bc..80c1c2f 100644
--- a/media/ndk/NdkMediaCodec.cpp
+++ b/media/ndk/NdkMediaCodec.cpp
@@ -116,7 +116,7 @@
 
         case kWhatStopActivityNotifications:
         {
-            uint32_t replyID;
+            sp<AReplyToken> replyID;
             msg->senderAwaitsResponse(&replyID);
 
             mCodec->mGeneration++;