Plumb a Browser->GPU surface destruction message for Android VDAs

content/common/gpu/media/avda_surface_tracker.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_COMMON_GPU_MEDIA_AVDA_SURFACE_TRACKER_H_
+#define CONTENT_COMMON_GPU_MEDIA_AVDA_SURFACE_TRACKER_H_
+
+#include <vector>
+
+#include "base/callback.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+using OnDestroyingSurfaceCallback = base::Callback<void(int)>;
+
+// AVDASurfaceTracker provides AndroidVideoDecodeAccelerators a way to register
+// callbacks that will be called when surfaces are destroyed. This is important
+// because Android SurfaceView Surfaces can be destroyed by the framework at any
+// time and we must stop rendering to them before returning from
+// onSurfaceDestroyed().
+// This is not thread safe. All access should be on the gpu main thread.

[Will Harris, 2016/04/22 23:31:09]

nit: if this is not thread safe it would be nice to see some DCHECK_CURRENTLY_ON
the right thread in the methods, just in case.

[watk, 2016/04/23 00:48:58]

Sounds good. Done with a ThreadChecker.

+// Callbacks will be run on the same thread.
+class AVDASurfaceTracker {
+ public:
+  AVDASurfaceTracker();
+  ~AVDASurfaceTracker();
+
+  static AVDASurfaceTracker* GetInstance();
+
+  void RegisterOnDestroyingSurfaceCallback(
+      const OnDestroyingSurfaceCallback& cb);
+
+  // Unregister a callback that was previously registered.
+  void UnregisterOnDestroyingSurfaceCallback(
+      const OnDestroyingSurfaceCallback& cb);
+
+  // Called in response to a message from the Browser indicating that the given
+  // surface is in the process of being destroyed.
+  void NotifyDestroyingSurface(int surface_id);
+
+ private:
+  std::vector<OnDestroyingSurfaceCallback> callbacks_;
+  DISALLOW_COPY_AND_ASSIGN(AVDASurfaceTracker);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_GPU_MEDIA_AVDA_SURFACE_TRACKER_H_