@Override
  public void onFailure(DataSource<Boolean> dataSource) {
    try {
      onFailureImpl(dataSource);
    } finally {
      dataSource.close();
    }
  }
Base implementation of {@link DataSubscriber} that ensures that the data source is closed when
the subscriber has finished with it.

<p>Sample usage:

<pre>
<code>
imagePipeline.isInDiskCache(
uri,
new BaseBooleanSubscriber() {
  public void onNewResultImpl(boolean isFound) {
    // caller's code here
  }
});
</code>
</pre>
fbcore/src/main/java/com/facebook/datasource/BaseBooleanSubscriber.java