HLS Live Streaming with DVR window and seek support added

[Problem]
Exoplayer does not support HLS Live streaming with DVR window and seek.

[Solution]
1. Support for available seek range added.
2. Support for seek within DVR window range added.

[Known Issues]
 1. Seeking beyond the live window is handled as follows:
    a. If the seek position is less than lower bound, we start playback from the first
available chunk data.
    b. If the seek position is greater than upper bound, we start giving data from the live
edge, however, exoplayer skips frames till it gets the data corresponding
to the seeked position

 2. We assume either media sequence or program date time is always present in the media playlist.
Playlists without media sequency or program date time is not handled. Behaviour is
unpredictable.

 3. Media playlist refresh time is aggresively fixed at half the target duration.
 We are yet to honor the spec that says if the last fetch did not change
 the playlist, try again after half the target duration, otherwise
 try after the target duration.

 4. We assume that playlist always have timezone in program date time or
 never have timezone.
 If this assumption fails, live DVR functionality will be broken.

[Tests]
1. Manifests with either program date time or media sequence or both tested.
2. Manifests with variable segment duration is tested.
2. Adaptive bitrate Switching tested. Also tested the case where available
range might be different across variants.

demo/src/main/java/com/google/android/exoplayer/demo/player/DemoPlayer.java

@@ -33,6 +33,7 @@
 import com.google.android.exoplayer.dash.DashChunkSource;
 import com.google.android.exoplayer.drm.StreamingDrmSessionManager;
 import com.google.android.exoplayer.extractor.ExtractorSampleSource;
+import com.google.android.exoplayer.hls.HlsChunkSource;
 import com.google.android.exoplayer.hls.HlsSampleSource;
 import com.google.android.exoplayer.metadata.MetadataTrackRenderer.MetadataRenderer;
 import com.google.android.exoplayer.metadata.id3.Id3Frame;
@@ -63,7 +64,8 @@ public class DemoPlayer implements ExoPlayer.Listener, ChunkSampleSource.EventLi
     SingleSampleSource.EventListener, DefaultBandwidthMeter.EventListener,
     MediaCodecVideoTrackRenderer.EventListener, MediaCodecAudioTrackRenderer.EventListener,
     StreamingDrmSessionManager.EventListener, DashChunkSource.EventListener, TextRenderer,
-    MetadataRenderer<List<Id3Frame>>, DebugTextViewHelper.Provider {
+    MetadataRenderer<List<Id3Frame>>, DebugTextViewHelper.Provider,
+    HlsChunkSource.EventListener {
 
   /**
    * Builds renderers for the player.
@@ -533,6 +535,9 @@ public void onAvailableRangeChanged(int sourceId, TimeRange availableRange) {
     if (infoListener != null) {
       infoListener.onAvailableRangeChanged(sourceId, availableRange);
     }
+    if (playerControl != null) {
+      playerControl.setAvailableRange(availableRange);
+    }
   }
 
   @Override

demo/src/main/java/com/google/android/exoplayer/demo/player/HlsRendererBuilder.java

@@ -147,7 +147,8 @@ public void onSingleManifest(HlsPlaylist manifest) {
       DataSource dataSource = new DefaultUriDataSource(context, bandwidthMeter, userAgent);
       HlsChunkSource chunkSource = new HlsChunkSource(true /* isMaster */, dataSource, url,
           manifest, DefaultHlsTrackSelector.newDefaultInstance(context), bandwidthMeter,
-          timestampAdjusterProvider, HlsChunkSource.ADAPTIVE_MODE_SPLICE);
+          timestampAdjusterProvider, HlsChunkSource.ADAPTIVE_MODE_SPLICE,
+              player.getMainHandler(), player, DemoPlayer.TYPE_VIDEO);
       HlsSampleSource sampleSource = new HlsSampleSource(chunkSource, loadControl,
           MAIN_BUFFER_SEGMENTS * BUFFER_SEGMENT_SIZE, mainHandler, player, DemoPlayer.TYPE_VIDEO);
       MediaCodecVideoTrackRenderer videoRenderer = new MediaCodecVideoTrackRenderer(context,
@@ -162,7 +163,8 @@ public void onSingleManifest(HlsPlaylist manifest) {
         DataSource audioDataSource = new DefaultUriDataSource(context, bandwidthMeter, userAgent);
         HlsChunkSource audioChunkSource = new HlsChunkSource(false /* isMaster */, audioDataSource,
             url, manifest, DefaultHlsTrackSelector.newAudioInstance(), bandwidthMeter,
-            timestampAdjusterProvider, HlsChunkSource.ADAPTIVE_MODE_SPLICE);
+            timestampAdjusterProvider, HlsChunkSource.ADAPTIVE_MODE_SPLICE,
+                player.getMainHandler(), player,DemoPlayer.TYPE_AUDIO);
         HlsSampleSource audioSampleSource = new HlsSampleSource(audioChunkSource, loadControl,
             AUDIO_BUFFER_SEGMENTS * BUFFER_SEGMENT_SIZE, mainHandler, player,
             DemoPlayer.TYPE_AUDIO);
@@ -182,7 +184,8 @@ public void onSingleManifest(HlsPlaylist manifest) {
         DataSource textDataSource = new DefaultUriDataSource(context, bandwidthMeter, userAgent);
         HlsChunkSource textChunkSource = new HlsChunkSource(false /* isMaster */, textDataSource,
             url, manifest, DefaultHlsTrackSelector.newSubtitleInstance(), bandwidthMeter,
-            timestampAdjusterProvider, HlsChunkSource.ADAPTIVE_MODE_SPLICE);
+            timestampAdjusterProvider, HlsChunkSource.ADAPTIVE_MODE_SPLICE,  null, null,
+            DemoPlayer.TYPE_VIDEO);
         HlsSampleSource textSampleSource = new HlsSampleSource(textChunkSource, loadControl,
             TEXT_BUFFER_SEGMENTS * BUFFER_SEGMENT_SIZE, mainHandler, player, DemoPlayer.TYPE_TEXT);
         textRenderer = new TextTrackRenderer(textSampleSource, player, mainHandler.getLooper());