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

content/browser/renderer_host/render_widget_host_view_aura.h

Index: content/browser/renderer_host/render_widget_host_view_aura.h
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index 31a60b1e3743ada498b4fbaa41f67255585ac216..df844ce5e93b25b1369dc887999edf00872482ed 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -24,7 +24,7 @@ class RenderWidgetHostView;
 }
 
 namespace gfx {
-class Canvas;
+class CanvasSkia;
 }
 
 namespace ui {
@@ -151,7 +151,7 @@ class RenderWidgetHostViewAura
   virtual ui::GestureStatus OnGestureEvent(aura::GestureEvent* event) OVERRIDE;
   virtual bool CanFocus() OVERRIDE;
   virtual void OnCaptureLost() OVERRIDE;
-  virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
+  virtual void OnPaint(gfx::CanvasSkia* canvas) OVERRIDE;
   virtual void OnWindowDestroying() OVERRIDE;
   virtual void OnWindowDestroyed() OVERRIDE;
   virtual void OnWindowVisibilityChanged(bool visible) OVERRIDE;
@@ -250,7 +250,7 @@ class RenderWidgetHostViewAura
   gfx::GLSurfaceHandle shared_surface_handle_;
 
   // If non-NULL we're in OnPaint() and this is the supplied canvas.
-  gfx::Canvas* paint_canvas_;
+  gfx::CanvasSkia* paint_canvas_;
 
   // Used to record the last position of the mouse.
   // While the mouse is locked, they store the last known position just as mouse