am 6a531717: size IMemoryHeap properly for screenshots

            sp<GraphicBuffer> buf(consumer->getCurrentBuffer());

            sw = buf->getWidth();

            sh = buf->getHeight();

            size_t size = buf->getStride() * sh * 4;

            size_t size = sw * sh * 4;

            // allocate shared memory large enough to hold the

            // screen capture