Allow CanvasSkia to bind to an existing SkCanvas.

views/native_theme_painter.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "views/native_theme_painter.h"
 
 #include "base/logging.h"
 #include "ui/base/animation/animation.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/canvas_skia.h"
@@ skipping 10 matching lines @@
 gfx::Size NativeThemePainter::GetPreferredSize() {
   const gfx::NativeTheme* theme = gfx::NativeTheme::instance();
   gfx::NativeTheme::ExtraParams extra;
   gfx::NativeTheme::State state = delegate_->GetThemeState(&extra);
   return theme->GetPartSize(delegate_->GetThemePart(), state, extra);
 }
 
 void NativeThemePainter::Paint(int w, int h, gfx::Canvas* canvas) {
   const gfx::NativeTheme* native_theme = gfx::NativeTheme::instance();
   gfx::NativeTheme::Part part = delegate_->GetThemePart();
-  gfx::CanvasSkia* skia_canvas = canvas->AsCanvasSkia();
   gfx::Rect rect(0, 0, w, h);
 
   if (delegate_->GetThemeAnimation() != NULL &&
       delegate_->GetThemeAnimation()->is_animating()) {
     // Paint background state.
     gfx::NativeTheme::ExtraParams prev_extra;
     gfx::NativeTheme::State prev_state =
         delegate_->GetBackgroundThemeState(&prev_extra);
-    native_theme->Paint(skia_canvas, part, prev_state, rect, prev_extra);
+    native_theme->Paint(
+        canvas->GetSkCanvas(), part, prev_state, rect, prev_extra);
 
     // Composite foreground state above it.
     gfx::NativeTheme::ExtraParams extra;
     gfx::NativeTheme::State state = delegate_->GetForegroundThemeState(&extra);
     int alpha = delegate_->GetThemeAnimation()->CurrentValueBetween(0, 255);
-    skia_canvas->SaveLayerAlpha(static_cast<uint8>(alpha));
-    native_theme->Paint(skia_canvas, part, state, rect, extra);
-    skia_canvas->Restore();
+    canvas->SaveLayerAlpha(static_cast<uint8>(alpha));
+    native_theme->Paint(canvas->GetSkCanvas(), part, state, rect, extra);
+    canvas->Restore();
   } else {
     gfx::NativeTheme::ExtraParams extra;
     gfx::NativeTheme::State state = delegate_->GetThemeState(&extra);
-    native_theme->Paint(skia_canvas, part, state, rect, extra);
+    native_theme->Paint(canvas->GetSkCanvas(), part, state, rect, extra);
   }
 }
 
 }  // namespace views