Make BaseMediaChunkOutput properly public

I think it was just wrong that it was package private before, since
it resulted in our public API referencing something that's not part
of the public API:

https://google.github.io/ExoPlayer/doc/reference/com/google/android/exoplayer2/source/chunk/BaseMediaChunk.html#init-com.google.android.exoplayer2.source.chunk.BaseMediaChunkOutput-

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=198396555

library/core/src/main/java/com/google/android/exoplayer2/source/chunk/BaseMediaChunkOutput.java

@@ -15,7 +15,6 @@
  */
  */
 package com.google.android.exoplayer2.source.chunk;
 package com.google.android.exoplayer2.source.chunk;
 
 
-import android.support.annotation.VisibleForTesting;
 import android.util.Log;
 import android.util.Log;
 import com.google.android.exoplayer2.extractor.DummyTrackOutput;
 import com.google.android.exoplayer2.extractor.DummyTrackOutput;
 import com.google.android.exoplayer2.extractor.TrackOutput;
 import com.google.android.exoplayer2.extractor.TrackOutput;
@@ -23,7 +22,6 @@ import com.google.android.exoplayer2.source.SampleQueue;
 import com.google.android.exoplayer2.source.chunk.ChunkExtractorWrapper.TrackOutputProvider;
 import com.google.android.exoplayer2.source.chunk.ChunkExtractorWrapper.TrackOutputProvider;
 
 
 /** An output for {@link BaseMediaChunk}s. */
 /** An output for {@link BaseMediaChunk}s. */
-@VisibleForTesting(otherwise = VisibleForTesting.PACKAGE_PRIVATE)
 public final class BaseMediaChunkOutput implements TrackOutputProvider {
 public final class BaseMediaChunkOutput implements TrackOutputProvider {
 
 
   private static final String TAG = "BaseMediaChunkOutput";
   private static final String TAG = "BaseMediaChunkOutput";