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/NuPlayerRenderer.h b/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.h
index 3a641a2..44c5d44 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.h
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.h
@@ -45,9 +45,9 @@
     void resume();
 
     enum {
-        kWhatEOS,
-        kWhatFlushComplete,
-        kWhatPosition,
+        kWhatEOS                = 'eos ',
+        kWhatFlushComplete      = 'fluC',
+        kWhatPosition           = 'posi',
     };
 
 protected:
@@ -57,14 +57,14 @@
 
 private:
     enum {
-        kWhatDrainAudioQueue,
-        kWhatDrainVideoQueue,
-        kWhatQueueBuffer,
-        kWhatQueueEOS,
-        kWhatFlush,
-        kWhatAudioSinkChanged,
-        kWhatPause,
-        kWhatResume,
+        kWhatDrainAudioQueue    = 'draA',
+        kWhatDrainVideoQueue    = 'draV',
+        kWhatQueueBuffer        = 'queB',
+        kWhatQueueEOS           = 'qEOS',
+        kWhatFlush              = 'flus',
+        kWhatAudioSinkChanged   = 'auSC',
+        kWhatPause              = 'paus',
+        kWhatResume             = 'resm',
     };
 
     struct QueueEntry {
@@ -102,8 +102,8 @@
 
     int64_t mLastPositionUpdateUs;
 
-    void onDrainAudioQueue();
-    void postDrainAudioQueue();
+    bool onDrainAudioQueue();
+    void postDrainAudioQueue(int64_t delayUs = 0);
 
     void onDrainVideoQueue();
     void postDrainVideoQueue();