Part of fix for double spins & faster startup

This change alters the way that the media player
interacts with the Widevine adaptive streaming buffer
logic.  It eliminates the reliance on cached buffer
duration to determine pause/play states and instead
only generates buffering events when the widevine
library is not producing data (i.e. when it is
buffering).  This eliminates unnecessary pause and
rebuffer cycles, reducing startup time and the
frequency and duration of spinners.

Multi-repo commit, depends on related changes in frameworks/av

Change-Id: I5b71f954268fbd390eed7f27db98a1bb470d5cfb
related-to-bug:6503294
related-to-bug:6463780

proprietary/wvm/include/WVMMediaSource.h

@@ -41,6 +41,7 @@ public:
     virtual status_t read(MediaBuffer **buffer, const ReadOptions *options = NULL);
 
     void addEncryptedSize(size_t size) { mEncryptedSizes.push_back(size); }
+    bool isStalled() const { return mIsStalled; }
 
     static int sLastError;
 
@@ -83,6 +84,7 @@ private:
     bool mIsLiveStream;
     bool mNewSegment;
     bool mCryptoInitialized;
+    bool mIsStalled;
 
     MediaBufferGroup *mGroup;