public void init(final String tag, final PerfListener perfListener) {
    mTag = Preconditions.checkNotNull(tag);
    mPerfListener = Preconditions.checkNotNull(perfListener);
  }
Tracks state of image request.

<p>Components that implement {@link Instrumented} interface can use this class to track their
requests.
samples/scrollperf/src/main/java/com/facebook/samples/scrollperf/instrumentation/Instrumentation.java