Various improvements to nuplayer playback

- Drastically cut down the number of times we supply the AudioSink with data
by estimating the time until the sink would run out of data and then scheduling
a refill in advance of that.

- Use a dedicated looper for video decoders since they are currently taking
too long to return from OMX_FillThisBuffer (bug 5325201)

- Revise thread priorities for the OMX dispatcher and software codecs, instead
of running them at ANDROID_PRIORITY_AUDIO, they now only run at
ANDROID_PRIORITY_FOREGROUND

- Since threads created by pthread_create inherit all of the parent threads
attributes including thread priority, briefly reset thread priority to
ANDROID_PRIORITY_FOREGROUND before instantiating OMX components and then
restore it.

Change-Id: If9332a3a20dad5485333d68c11de0d2d5d3fffc3
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.h b/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.h
index fabc606..3ab1fcf 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.h
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.h
@@ -43,13 +43,14 @@
 
 private:
     enum {
-        kWhatCodecNotify,
+        kWhatCodecNotify        = 'cdcN',
     };
 
     sp<AMessage> mNotify;
     sp<NativeWindowWrapper> mNativeWindow;
 
     sp<ACodec> mCodec;
+    sp<ALooper> mCodecLooper;
 
     Vector<sp<ABuffer> > mCSD;
     size_t mCSDIndex;