Use a custom video renderer for MetadataRetrieverImpl.

Currently, MetadataRetrieverImpl uses MediaCodecVideoRenderer to renderering
frames to capture. It suffers from 2 issues:
- MediaCodecVideoRenderer has a lot of logic to time frame release, including
drop frames if late or try to keep up with feeding speed etc... These are not
necessary at all for frame retrieval.
- MediaCodecVideoRenderer always tries to render 1 frame after video surface
update. This may some times lead to the wrong image being rendered for
MetadataRetriever.
This CL replaces this with a custom video renderer, that does not time frame
releases, and only render first frame after position reset / renderer
re-enabling.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=207276937

library/core/src/main/java/com/google/android/exoplayer2/video/MediaCodecVideoRenderer.java

@@ -685,6 +685,15 @@ public class MediaCodecVideoRenderer extends MediaCodecRenderer {
   }
   }
 
 
   /**
   /**
+   * Returns the offset that should be subtracted from {@code bufferPresentationTimeUs} in {@link
+   * #processOutputBuffer(long, long, MediaCodec, ByteBuffer, int, int, long, boolean)} to get the
+   * playback position with respect to the media.
+   */
+  protected long getOutputStreamOffsetUs() {
+    return outputStreamOffsetUs;
+  }
+
+  /**
    * Called when an output buffer is successfully processed.
    * Called when an output buffer is successfully processed.
    *
    *
    * @param presentationTimeUs The timestamp associated with the output buffer.
    * @param presentationTimeUs The timestamp associated with the output buffer.