SF: Make screenshot surface async

    // create a surface (because we're a producer, and we need to

    // dequeue/queue a buffer)

    sp<Surface> sur = new Surface(producer, false);

    // Put the screenshot Surface into async mode so that

    // Layer::headFenceHasSignaled will always return true and we'll latch the

    // first buffer regardless of whether or not its acquire fence has

    // signaled. This is needed to avoid a race condition in the rotation

    // animation. See b/30209608

    sur->setAsyncMode(true);

    ANativeWindow* window = sur.get();

    status_t result = native_window_api_connect(window, NATIVE_WINDOW_API_EGL);