ui: Cache the output of View::OnPaint when the View isn't invalid.

ui/compositor/paint_recorder.h

Index: ui/compositor/paint_recorder.h
diff --git a/ui/compositor/paint_recorder.h b/ui/compositor/paint_recorder.h
index 7c3df82b9056b71191e1c666e1db89da2a81cc0a..4f5c1cba205765719865a34f6f5726aeefc1f6ed 100644
--- a/ui/compositor/paint_recorder.h
+++ b/ui/compositor/paint_recorder.h
@@ -22,6 +22,7 @@ class SkCanvas;
 class SkPictureRecorder;
 
 namespace ui {
+class PaintCache;
 class PaintContext;
 
 // A class to hide the complexity behind setting up a recording into a
@@ -30,6 +31,7 @@ class PaintContext;
 // recording is complete and can be cached.
 class COMPOSITOR_EXPORT PaintRecorder {
  public:
+  PaintRecorder(const PaintContext& context, PaintCache* cache);

[sky, 2015/04/23 16:29:00]

Document ownership/lifetime of PaintCache.

[danakj, 2015/04/23 16:34:09]

OK. To me raw pointer implies weak pointer that you don't own, but I'll add a
comment saying so.

   explicit PaintRecorder(const PaintContext& context);
   ~PaintRecorder();
 
@@ -40,6 +42,7 @@ class COMPOSITOR_EXPORT PaintRecorder {
   const PaintContext& context_;
   gfx::Canvas* canvas_;
   scoped_ptr<gfx::Canvas> owned_canvas_;
+  PaintCache* cache_;
 
   DISALLOW_COPY_AND_ASSIGN(PaintRecorder);
 };