nuplayer: fixes for subtitle pause/resume

- pause after the current block when select track
- ignore metadata timestamps as they're too sparse
- use smaller range when searching for next segment to prevent
  resumeUntil from downloading too much data

bug: 20500732
Change-Id: Ibda57a39ec86efd96a8dd0db95adeb92d076697a
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayer.cpp b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
index 9963353..63b12a9 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
@@ -189,7 +189,8 @@
       mVideoFpsHint(-1.f),
       mStarted(false),
       mPaused(false),
-      mPausedByClient(false) {
+      mPausedByClient(false),
+      mPausedForBuffering(false) {
     clearFlushComplete();
 }
 
@@ -671,7 +672,10 @@
         {
             ALOGV("kWhatStart");
             if (mStarted) {
-                onResume();
+                // do not resume yet if the source is still buffering
+                if (!mPausedForBuffering) {
+                    onResume();
+                }
             } else {
                 onStart();
             }
@@ -1977,9 +1981,10 @@
         case Source::kWhatPauseOnBufferingStart:
         {
             // ignore if not playing
-            if (mStarted && !mPausedByClient) {
+            if (mStarted) {
                 ALOGI("buffer low, pausing...");
 
+                mPausedForBuffering = true;
                 onPause();
             }
             // fall-thru
@@ -1994,10 +1999,15 @@
         case Source::kWhatResumeOnBufferingEnd:
         {
             // ignore if not playing
-            if (mStarted && !mPausedByClient) {
+            if (mStarted) {
                 ALOGI("buffer ready, resuming...");
 
-                onResume();
+                mPausedForBuffering = false;
+
+                // do not resume yet if client didn't unpause
+                if (!mPausedByClient) {
+                    onResume();
+                }
             }
             // fall-thru
         }