Merge "graphics: discard stale data from message queue" into oc-mr1-dev

    bool writeQueue(bool* outQueueChanged, uint32_t* outCommandLength,

            hidl_vec<hidl_handle>* outCommandHandles)

    {

        // After data are written to the queue, it may not be read by the

        // remote reader when

        //

        //  - the writer does not send them (because of other errors)

        //  - the hwbinder transaction fails

        //  - the reader does not read them (because of other errors)

        //

        // Discard the stale data here.

        size_t staleDataSize = mQueue ? mQueue->availableToRead() : 0;

        if (staleDataSize > 0) {

            ALOGW("discarding stale data from message queue");

            CommandQueueType::MemTransaction tx;

            if (mQueue->beginRead(staleDataSize, &tx)) {

                mQueue->commitRead(staleDataSize);

            }

        }

        // write data to queue, optionally resizing it

        if (mQueue && (mDataMaxSize <= mQueue->getQuantumCount())) {

            if (!mQueue->write(mData.get(), mDataWritten)) {