hle: nvflinger: Add ProducerListener interface.

src/core/CMakeLists.txt

@@ -541,6 +541,7 @@ add_library(core STATIC
     hle/service/nvflinger/nvflinger.cpp
     hle/service/nvflinger/nvflinger.h
     hle/service/nvflinger/pixel_format.h
+    hle/service/nvflinger/producer_listener.h
     hle/service/nvflinger/status.h
     hle/service/nvflinger/ui/fence.h
     hle/service/nvflinger/ui/graphic_buffer.h

src/core/hle/service/nvflinger/producer_listener.h

@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright 2021 yuzu Emulator Project
+// Copyright 2014 The Android Open Source Project
+// Parts of this implementation were base on:
+// https://cs.android.com/android/platform/superproject/+/android-5.1.1_r38:frameworks/native/include/gui/IProducerListener.h
+
+#pragma once
+
+namespace android {
+
+class IProducerListener {
+public:
+    virtual void OnBufferReleased() = 0;
+};
+
+} // namespace android