Merge "BlastBufferQueue: Fix async worker deadlock" am: 09fe4d2c

        std::unique_lock<std::mutex> lock(mMutex);

        while (!mDone) {

            while (!mRunnables.empty()) {

                std::function<void()> runnable = mRunnables.front();

                mRunnables.pop_front();

                runnable();

                std::deque<std::function<void()>> runnables = std::move(mRunnables);

                mRunnables.clear();

                lock.unlock();

                // Run outside the lock since the runnable might trigger another

                // post to the async worker.

                execute(runnables);

                lock.lock();

            }

            mCv.wait(lock);

        }

    }

    void execute(std::deque<std::function<void()>>& runnables) {

        while (!runnables.empty()) {

            std::function<void()> runnable = runnables.front();

            runnables.pop_front();

            runnable();

        }

    }

public:

    AsyncWorker() : Singleton<AsyncWorker>() { mThread = std::thread(&AsyncWorker::run, this); }