am 5e5efde7: BufferQueue: add a check for the max acquired bufs

status_t BufferQueue::acquireBuffer(BufferItem *buffer) {

    ATRACE_CALL();

    Mutex::Autolock _l(mMutex);

    // Check that the consumer doesn't currently have the maximum number of

    // buffers acquired.  We allow the max buffer count to be exceeded by one

    // buffer, so that the consumer can successfully set up the newly acquired

    // buffer before releasing the old one.

    int numAcquiredBuffers = 0;

    for (int i = 0; i < NUM_BUFFER_SLOTS; i++) {

        if (mSlots[i].mBufferState == BufferSlot::ACQUIRED) {

            numAcquiredBuffers++;

        }

    }

    if (numAcquiredBuffers >= mMaxAcquiredBufferCount+1) {

        ST_LOGE("acquireBuffer: max acquired buffer count reached: %d (max=%d)",

                numAcquiredBuffers, mMaxAcquiredBufferCount);

        return INVALID_OPERATION;

    }

    // check if queue is empty

    // In asynchronous mode the list is guaranteed to be one buffer

    // deep, while in synchronous mode we use the oldest buffer.