docs: public Task<Void> clearAll() {
      mStagingArea.clearAll();
      try {
        return Task.call(
            new Callable<Void>() {
              @Override
              public Void call() throws Exception {
                mStagingArea.clearAll();
                mFileCache.clearAll();
                return null;
              }
            },
            mWriteExecutor);
      } catch (Exception exception) {
        // Log failure
        // TODO: 3697790
        FLog.w(TAG, exception, "Failed to schedule disk-cache clear");
        return Task.forError(exception);
      }
    }