code: public int getSize() {
      if (mPooledByteBufferRef != null && mPooledByteBufferRef.get() != null) {
        return mPooledByteBufferRef.get().size();
      }
      return mStreamSize;
    }
docs: Returns the size of the backing structure.
  
  <p> If it's a PooledByteBuffer returns its size if its not null, -1 otherwise. If it's an
  InputStream, return the size if it was set, -1 otherwise.