cc: Split and comment methods for Display vs LayerTreeHostImpl

cc/output/output_surface_client.h

Index: cc/output/output_surface_client.h
diff --git a/cc/output/output_surface_client.h b/cc/output/output_surface_client.h
index 472fcc3fa2193e96e4e08d115e363b3da07a40a4..cd91919e6c40cf0cbcb809fe3af1e4d5242027cb 100644
--- a/cc/output/output_surface_client.h
+++ b/cc/output/output_surface_client.h
@@ -25,22 +25,22 @@ struct ManagedMemoryPolicy;
 
 class CC_EXPORT OutputSurfaceClient {
  public:
-  // Pass the begin frame source for the client to observe.  Client does not own
-  // the BeginFrameSource.  OutputSurface should call this once after binding to
-  // the client and then call again with a null while detaching.
-  virtual void SetBeginFrameSource(BeginFrameSource* source) = 0;
+  // ============== DISPLAY COMPOSITOR ONLY =======================
 
+  // From surfaceless/ozone browser compositor output surface.
   virtual void SetNeedsRedrawRect(const gfx::Rect& damage_rect) = 0;
-  // For LayerTreeHostImpl, this is more of a OnSwapBuffersAck from the display
-  // compositor that it received and will use the frame, unblocking it from
-  // producing more frames.
-  // For the display compositor this is literally a notification that the swap
-  // to the hardware is complete.
-  virtual void DidSwapBuffersComplete() = 0;
+  // For overlays.
   virtual void DidReceiveTextureInUseResponses(
       const gpu::TextureInUseResponses& responses) = 0;
+
+  // ============== LAYER TREE COMPOSITOR ONLY ====================
+
+  // Pass the begin frame source for the client to observe.  Client does not own
+  // the BeginFrameSource.  OutputSurface should call this once after binding to
+  // the client and then call again with a null while detaching.
+  virtual void SetBeginFrameSource(BeginFrameSource* source) = 0;
   virtual void ReclaimResources(const ReturnedResourceArray& resources) = 0;
-  virtual void DidLoseOutputSurface() = 0;
+  // For WebView.
   virtual void SetExternalTilePriorityConstraints(
       const gfx::Rect& viewport_rect,
       const gfx::Transform& transform) = 0;
@@ -57,6 +57,19 @@ class CC_EXPORT OutputSurfaceClient {
   // can use without changing visibility.
   virtual void SetMemoryPolicy(const ManagedMemoryPolicy& policy) = 0;
 
+  // ============== BOTH TYPES OF COMPOSITOR ======================
+
+  // For LayerTreeHostImpl, this is more of a OnSwapBuffersAck from the display
+  // compositor that it received and will use the frame, unblocking it from
+  // producing more frames.
+  // For the display compositor this is literally a notification that the swap
+  // to the hardware is complete.
+  virtual void DidSwapBuffersComplete() = 0;
+
+  // Needs thought, if LTHI has only context providers, it needs to register a
+  // lost callback, so we need to support multiple callbacks.
+  virtual void DidLoseOutputSurface() = 0;
+
  protected:
   virtual ~OutputSurfaceClient() {}
 };