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/NuPlayer.cpp b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
index ee77f47..6f34ba7 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
@@ -299,7 +299,12 @@
                          sampleRate, numChannels);
 
                     mAudioSink->close();
-                    CHECK_EQ(mAudioSink->open(sampleRate, numChannels), (status_t)OK);
+                    CHECK_EQ(mAudioSink->open(
+                                sampleRate,
+                                numChannels,
+                                AUDIO_FORMAT_PCM_16_BIT,
+                                8 /* bufferCount */),
+                             (status_t)OK);
                     mAudioSink->start();
 
                     mRenderer->signalAudioSinkChanged();