@Override
  public int getTimestampMsForFrame(int frameNumber) {
    return frameNumber == 0 ? 0 : mAccumulatedDurationsMs[frameNumber - 1];
  }
Implementation of {@link AnimatedDrawableBackend} for unit tests.
animated-base/src/test/java/com/facebook/imagepipeline/animated/testing/TestAnimatedDrawableBackend.java