Support high dpi in menu scroll arrow, submenu arrow and drag_utils.

ui/gfx/image/canvas_image_source.h

+// Copyright (c) 2012 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.
+
+#ifndef UI_GFX_IMAGE_CANVAS_IMAGE_SOURCE_H_
+#define UI_GFX_IMAGE_CANVAS_IMAGE_SOURCE_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "ui/base/ui_export.h"
+#include "ui/gfx/image/image_skia_source.h"
+#include "ui/gfx/size.h"
+
+namespace gfx {
+class Canvas;
+class ImageSkiaRep;
+
+// CanvasImageSource is useful if you need to generate an image for
+// a scale factor using gfx::Canvas. It creates a new Canvas
+// with target scale factor and generates ImageSkiaRep when drawing is
+// completed.
+class UI_EXPORT CanvasImageSource : public gfx::ImageSkiaSource {
+ public:
+  CanvasImageSource(const gfx::Size& size, bool is_opaque);
+
+  // Called when a new image needs to be drawn for a scale factor.
+  virtual void Draw(gfx::Canvas* canvas) = 0;
+
+  // Returns the size of images in DIP that this source will generate.
+  const gfx::Size& size() const { return size_; };
+
+  // Overridden from gfx::ImageSkiaSource.
+  virtual gfx::ImageSkiaRep GetImageForScale(
+      ui::ScaleFactor scale_factor) OVERRIDE;
+
+ protected:
+  virtual ~CanvasImageSource() {}
+
+  const gfx::Size size_;
+  const bool is_opaque_;
+  DISALLOW_COPY_AND_ASSIGN(CanvasImageSource);
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_IMAGE_CANVAS_IMAGE_SOURCE_H_