[automerger] Fix a race condition in OMXNodeInstance am: fe3708f7

    }

    BufferMeta *buffer_meta = static_cast<BufferMeta *>(header->pAppPrivate);

    // Invalidate buffers in the client side first before calling OMX_FreeBuffer.

    // If not, pending events in the client side might access the buffers after free.

    invalidateBufferID(buffer);

    OMX_ERRORTYPE err = OMX_FreeBuffer(mHandle, portIndex, header);

    CLOG_IF_ERROR(freeBuffer, err, "%s:%u %#x", portString(portIndex), portIndex, buffer);

    delete buffer_meta;

    buffer_meta = NULL;

    invalidateBufferID(buffer);

    return StatusFromOMXError(err);

}