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

ui/views/widget/native_widget_delegate.h

Index: ui/views/widget/native_widget_delegate.h
diff --git a/ui/views/widget/native_widget_delegate.h b/ui/views/widget/native_widget_delegate.h
index 4fac0b0d2db40c4e8e75236b92ff6166e9457149..9fa82d0c333dba1235906dd2d95541ae562dc89a 100644
--- a/ui/views/widget/native_widget_delegate.h
+++ b/ui/views/widget/native_widget_delegate.h
@@ -10,7 +10,7 @@
 #include "ui/views/views_export.h"
 
 namespace gfx {
-class Canvas;
+class CanvasSkia;
 class Point;
 class Size;
 }
@@ -89,7 +89,7 @@ class VIEWS_EXPORT NativeWidgetDelegate {
 
   // Paints the rootview in the canvas. This will also refresh the compositor
   // tree if necessary when accelerated painting is enabled.
-  virtual void OnNativeWidgetPaint(gfx::Canvas* canvas) = 0;
+  virtual void OnNativeWidgetPaint(gfx::CanvasSkia* canvas) = 0;
 
   // Returns the non-client component (see ui/base/hit_test.h) containing
   // |point|, in client coordinates.