@Override
  public synchronized int getInUseSizeInBytes() {
    return mCachedEntries.getSizeInBytes() - mExclusiveEntries.getSizeInBytes();
  }
Gets the total size in bytes of the cached items that are used by at least one client.
imagepipeline-base/src/main/java/com/facebook/imagepipeline/cache/LruCountingMemoryCache.java