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

ui/views/bubble/bubble_border.h

Index: ui/views/bubble/bubble_border.h
diff --git a/ui/views/bubble/bubble_border.h b/ui/views/bubble/bubble_border.h
index 288485ea9405efe192794cf50c0a03402fe453ea..28fdfc1af8b8999278235bf5450ce40bc9d5de47 100644
--- a/ui/views/bubble/bubble_border.h
+++ b/ui/views/bubble/bubble_border.h
@@ -128,9 +128,9 @@ class VIEWS_EXPORT BubbleBorder : public views::Border {
 
   // Overridden from views::Border:
   virtual void Paint(const views::View& view,
-                     gfx::Canvas* canvas) const OVERRIDE;
+                     gfx::CanvasSkia* canvas) const OVERRIDE;
 
-  void DrawEdgeWithArrow(gfx::Canvas* canvas,
+  void DrawEdgeWithArrow(gfx::CanvasSkia* canvas,
                          bool is_horizontal,
                          SkBitmap* edge,
                          SkBitmap* arrow,
@@ -140,7 +140,7 @@ class VIEWS_EXPORT BubbleBorder : public views::Border {
                          int after_arrow,
                          int offset) const;
 
-  void DrawArrowInterior(gfx::Canvas* canvas,
+  void DrawArrowInterior(gfx::CanvasSkia* canvas,
                          bool is_horizontal,
                          int tip_x,
                          int tip_y,
@@ -178,7 +178,7 @@ class VIEWS_EXPORT BubbleBackground : public views::Background {
   explicit BubbleBackground(BubbleBorder* border) : border_(border) {}
 
   // Background overrides.
-  virtual void Paint(gfx::Canvas* canvas, views::View* view) const OVERRIDE;
+  virtual void Paint(gfx::CanvasSkia* canvas, views::View* view) const OVERRIDE;
 
  private:
   BubbleBorder* border_;