Mozart: Improve tracing and backpressure.

services/gfx/compositor/render/render_frame.h

Index: services/gfx/compositor/render/render_frame.h
diff --git a/services/gfx/compositor/render/render_frame.h b/services/gfx/compositor/render/render_frame.h
index 334e690aaee64c410b2e6969713078e3418ba24d..f468fb949b131566c36f926a2536b427666d9753 100644
--- a/services/gfx/compositor/render/render_frame.h
+++ b/services/gfx/compositor/render/render_frame.h
@@ -22,28 +22,43 @@ namespace compositor {
 // They have no direct references to the scene graph.
 class RenderFrame : public base::RefCountedThreadSafe<RenderFrame> {
  public:
+  // Contains metadata about a particular |RenderFrame| used for tracing
+  // and statistics.
+  class Metadata {
+   public:
+    Metadata(const mojo::gfx::composition::FrameInfo& frame_info,
+             int64_t composition_time);
+    ~Metadata();
+
+    const mojo::gfx::composition::FrameInfo& frame_info() const {
+      return frame_info_;
+    }
+    int64_t composition_time() const { return composition_time_; }
+
+   private:
+    mojo::gfx::composition::FrameInfo frame_info_;
+    int64_t composition_time_;
+  };
+
   // Creates an empty render frame with no content.
-  RenderFrame(const SkIRect& viewport,
-              const mojo::gfx::composition::FrameInfo& frame_info);
+  RenderFrame(const Metadata& metadata, const SkIRect& viewport);
 
   // Creates render frame backed by a picture.
-  RenderFrame(const SkIRect& viewport,
-              const mojo::gfx::composition::FrameInfo& frame_info,
+  RenderFrame(const Metadata& metadata,
+              const SkIRect& viewport,
               const skia::RefPtr<SkPicture>& picture);
 
+  // Gets metadata about the frame.
+  const Metadata& metadata() const { return metadata_; }
+
   // Gets the frame's viewport in pixels.
   const SkIRect& viewport() const { return viewport_; }
 
-  // Gets information about the frame to be rendered.
-  const mojo::gfx::composition::FrameInfo& frame_info() const {
-    return frame_info_;
-  }
-
   // Gets the underlying picture to rasterize, or null if the frame is empty.
   const skia::RefPtr<SkPicture>& picture() const { return picture_; }
 
-  // Paints the frame to a canvas.
-  void Paint(SkCanvas* canvas) const;
+  // Draws the contents of the frame to a canvas.
+  void Draw(SkCanvas* canvas) const;
 
  private:
   friend class base::RefCountedThreadSafe<RenderFrame>;
@@ -51,8 +66,8 @@ class RenderFrame : public base::RefCountedThreadSafe<RenderFrame> {
 
   ~RenderFrame();
 
+  Metadata metadata_;
   SkIRect viewport_;
-  mojo::gfx::composition::FrameInfo frame_info_;
   skia::RefPtr<SkPicture> picture_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrame);