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

ui/gfx/image/canvas_image_source.cc

+// 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.
+
+#include "ui/gfx/image/canvas_image_source.h"
+
+#include "base/logging.h"
+#include "ui/gfx/canvas.h"
+#include "ui/base/layout.h"
+
+namespace gfx {
+
+////////////////////////////////////////////////////////////////////////////////
+// CanvasImageSource
+
+CanvasImageSource::CanvasImageSource(const gfx::Size& size, bool is_opaque)
+    : size_(size),
+      is_opaque_(is_opaque) {
+}
+
+gfx::ImageSkiaRep CanvasImageSource::GetImageForScale(
+    ui::ScaleFactor scale_factor) {
+  gfx::Canvas canvas(size_, scale_factor, is_opaque_);
+  Draw(&canvas);
+  return canvas.ExtractImageSkiaRep();
+}
+
+}  // namespace gfx