Implements core logic for Pixel Canvas

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 3785c1bbc2359c5bd590609db370a7a426baacfe..5104612dea1b4f279b25c6713662f460c8dd3def 100644
--- a/ui/compositor/paint_recorder.h
+++ b/ui/compositor/paint_recorder.h
@@ -29,9 +29,11 @@ class COMPOSITOR_EXPORT PaintRecorder {
  public:
   // The |cache| is owned by the caller and must be kept alive while
   // PaintRecorder is in use. Canvas is bounded by |recording_size|.
+  // |recording_size| should be in pixels if pixel canvas is enabled.
   PaintRecorder(const PaintContext& context,
                 const gfx::Size& recording_size,
                 PaintCache* cache);
+  // |recording_size| should always be in DIPs.
   PaintRecorder(const PaintContext& context, const gfx::Size& recording_size);
   ~PaintRecorder();