NOT for review (for discussion): Query IOSurfaceIsInUse in the browser process

cc/output/gl_renderer.h

Index: cc/output/gl_renderer.h
diff --git a/cc/output/gl_renderer.h b/cc/output/gl_renderer.h
index 07ede049a7274ee93edda2d37c7e425dc0b1d36c..3c39593282c3a76a5fd79196b9e321823d917fd9 100644
--- a/cc/output/gl_renderer.h
+++ b/cc/output/gl_renderer.h
@@ -264,24 +264,36 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
       gfx::RectF* new_bounds);
 
   // Schedules the |ca_layer_overlay|, which is guaranteed to have a non-null
-  // |rpdq| parameter.
-  void ScheduleRenderPassDrawQuad(const CALayerOverlay* ca_layer_overlay,
-                                  DrawingFrame* external_frame);
+  // |rpdq| parameter. Returns the resource lock for the layer contents.
+  std::unique_ptr<ResourceProvider::ScopedReadLockGL>
+  ScheduleRenderPassDrawQuad(const CALayerOverlay* ca_layer_overlay,
+                             DrawingFrame* external_frame);
 
   using OverlayResourceLock =
       std::unique_ptr<ResourceProvider::ScopedReadLockGL>;
   using OverlayResourceLockList = std::vector<OverlayResourceLock>;
 
+  // A resource lock for a resource that was used by ScheduleCALayer. The
+  // resource can only be unlocked once its GpuMemoryBuffer is no longer in
+  // use.
+  struct CALayerResourceLock {
+    CALayerResourceLock();
+    ~CALayerResourceLock();
+    CALayerResourceLock(CALayerResourceLock&& ca_layer_resource);
+
+    uint32_t outstanding_ack_count = 0;
+    std::unique_ptr<ResourceProvider::ScopedReadLockGL> lock;
+    std::unique_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer;
+    bool in_use_valid = false;
+  };
+  std::map<unsigned, CALayerResourceLock> ca_layer_resources_;
+
   // Resources that have been sent to the GPU process, but not yet swapped.
   OverlayResourceLockList pending_overlay_resources_;
 
   // Resources that should be shortly swapped by the GPU process.
   std::deque<OverlayResourceLockList> swapping_overlay_resources_;
 
-  // Resources that the GPU process has finished swapping. The key is the
-  // texture id of the resource.
-  std::map<unsigned, OverlayResourceLock> swapped_and_acked_overlay_resources_;
-
   unsigned offscreen_framebuffer_id_;
 
   std::unique_ptr<StaticGeometryBinding> shared_geometry_;