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

ui/views/controls/textfield/textfield.cc

Index: ui/views/controls/textfield/textfield.cc
diff --git a/ui/views/controls/textfield/textfield.cc b/ui/views/controls/textfield/textfield.cc
index 15f802807b76b08d61ff57654e7fcd5311d7d424..23a17c60244466cf416d230b001d3ca7fcc72644 100644
--- a/ui/views/controls/textfield/textfield.cc
+++ b/ui/views/controls/textfield/textfield.cc
@@ -381,12 +381,12 @@ bool Textfield::SkipDefaultKeyEventProcessing(const KeyEvent& e) {
   return false;
 }
 
-void Textfield::OnPaintBackground(gfx::Canvas* canvas) {
+void Textfield::OnPaintBackground(gfx::CanvasSkia* canvas) {
   // Overridden to be public - gtk_views_entry.cc wants to call it.
   View::OnPaintBackground(canvas);
 }
 
-void Textfield::OnPaintFocusBorder(gfx::Canvas* canvas) {
+void Textfield::OnPaintFocusBorder(gfx::CanvasSkia* canvas) {
   if (NativeViewHost::kRenderNativeControlFocus)
     View::OnPaintFocusBorder(canvas);
 }