ui/gfx: Make gfx::Canvas inherit from gfx::CanvasSkia.

ui/views/widget/widget.h

Index: ui/views/widget/widget.h
diff --git a/ui/views/widget/widget.h b/ui/views/widget/widget.h
index 527914a886c5fc2b8a21dd0fcc360ce50db32df9..90c2d80f6076eec0898324642a64667b040f1e02 100644
--- a/ui/views/widget/widget.h
+++ b/ui/views/widget/widget.h
@@ -35,7 +35,7 @@
 #endif
 
 namespace gfx {
-class Canvas;
+class CanvasSkia;
 class Point;
 class Rect;
 }
@@ -623,7 +623,7 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
   virtual bool HasFocusManager() const OVERRIDE;
   virtual bool OnNativeWidgetPaintAccelerated(
       const gfx::Rect& dirty_region) OVERRIDE;
-  virtual void OnNativeWidgetPaint(gfx::Canvas* canvas) OVERRIDE;
+  virtual void OnNativeWidgetPaint(gfx::CanvasSkia* canvas) OVERRIDE;
   virtual int GetNonClientComponent(const gfx::Point& point) OVERRIDE;
   virtual bool OnKeyEvent(const KeyEvent& event) OVERRIDE;
   virtual bool OnMouseEvent(const MouseEvent& event) OVERRIDE;