Modified CeaDecoder and CeaSubtitle so that it's correctly setting the…

Modified CeaDecoder and CeaSubtitle so that it's correctly setting the subsampleOffset and making proper use of it.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=145552166

library/src/main/java/com/google/android/exoplayer2/text/cea/CeaDecoder.java

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.text.cea;
 
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.text.Subtitle;
 import com.google.android.exoplayer2.text.SubtitleDecoder;
 import com.google.android.exoplayer2.text.SubtitleDecoderException;
@@ -109,7 +110,7 @@ import java.util.TreeSet;
         Subtitle subtitle = createSubtitle();
         if (!inputBuffer.isDecodeOnly()) {
           SubtitleOutputBuffer outputBuffer = availableOutputBuffers.pollFirst();
-          outputBuffer.setContent(inputBuffer.timeUs, subtitle, 0);
+          outputBuffer.setContent(inputBuffer.timeUs, subtitle, Format.OFFSET_SAMPLE_RELATIVE);
           releaseInputBuffer(inputBuffer);
           return outputBuffer;
         }

library/src/main/java/com/google/android/exoplayer2/text/cea/CeaSubtitle.java

@@ -15,8 +15,11 @@
  */
 package com.google.android.exoplayer2.text.cea;
 
+import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.text.Cue;
 import com.google.android.exoplayer2.text.Subtitle;
+import com.google.android.exoplayer2.util.Assertions;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -35,7 +38,7 @@ import java.util.List;
 
   @Override
   public int getNextEventTimeIndex(long timeUs) {
-    return 0;
+    return timeUs < 0 ? 0 : C.INDEX_UNSET;
   }
 
   @Override
@@ -45,12 +48,13 @@ import java.util.List;
 
   @Override
   public long getEventTime(int index) {
+    Assertions.checkArgument(index == 0);
     return 0;
   }
 
   @Override
   public List<Cue> getCues(long timeUs) {
-    return cues;
+    return timeUs >= 0 ? cues : Collections.<Cue>emptyList();
   }
 
 }