Mozart: Improve tracing and backpressure.

services/gfx/compositor/compositor_engine.h

 // Copyright 2015 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 SERVICES_GFX_COMPOSITOR_COMPOSITOR_H_
 #define SERVICES_GFX_COMPOSITOR_COMPOSITOR_H_
 
 #include <unordered_map>
 #include <vector>
 
@@ skipping 71 matching lines @@
   void OnSceneConnectionError(SceneState* scene_state);
   void DestroyScene(SceneState* scene_state);
 
   void OnRendererConnectionError(RendererState* renderer_state);
   void DestroyRenderer(RendererState* renderer_state);
 
   void InvalidateScene(SceneState* scene_state);
   SceneDef::Disposition PresentScene(SceneState* scene_state,
                                      int64_t presentation_time);
 
+  // Starts the process of composing the contents of the renderer to
+  // produce a new frame.
+  void ComposeRenderer(RendererState* renderer_state,
+                       const mojo::gfx::composition::FrameInfo& frame_info);
+
+  // Applies and validates scene updates from all scenes which are included
+  // in the renderer's scene graph.
   void PresentRenderer(RendererState* renderer_state,
                        int64_t presentation_time);
-  void SnapshotRenderer(RendererState* renderer_state,
-                        const mojo::gfx::composition::FrameInfo& frame_info);
+
+  // Resolves scene dependencies and captures a snapshot of the current
+  // state of the renderer's scene graph.
+  void SnapshotRenderer(RendererState* renderer_state);
   void SnapshotRendererInner(RendererState* renderer_state,
                              std::ostream* block_log);
+
+  // Paints the renderer's current snapshot and submits a frame of content
+  // to the output for display.
+  void PaintRenderer(RendererState* renderer_state,
+                     const mojo::gfx::composition::FrameInfo& frame_info,
+                     int64_t composition_time);
+
+  // Schedules the next frame to be rendered, if needed.
   void ScheduleFrameForRenderer(RendererState* renderer_state,
                                 Scheduler::SchedulingMode scheduling_mode);
 
   void OnOutputError(const base::WeakPtr<RendererState>& renderer_state_weak);
   void OnOutputUpdateRequest(
       const base::WeakPtr<RendererState>& renderer_state_weak,
       const mojo::gfx::composition::FrameInfo& frame_info);
   void OnOutputSnapshotRequest(
       const base::WeakPtr<RendererState>& renderer_state_weak,
       const mojo::gfx::composition::FrameInfo& frame_info);
@@ skipping 25 matching lines @@
   Universe universe_;
 
   base::WeakPtrFactory<CompositorEngine> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CompositorEngine);
 };
 
 }  // namespace compositor
 
 #endif  // SERVICES_GFX_COMPOSITOR_COMPOSITOR_H_