Introduce ui::PaintRecorder and use it for CursorWindowDelegate.

ui/compositor/paint_recorder.h

+// Copyright 2015 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_COMPOSITOR_PAINT_RECORDER_H_
+#define UI_COMPOSITOR_PAINT_RECORDER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "skia/ext/refptr.h"
+#include "third_party/skia/include/core/SkPictureRecorder.h"
+#include "ui/compositor/compositor_export.h"
+
+namespace cc {
+class DisplayItemList;
+class DrawingDisplayItem;
+}
+
+namespace gfx {
+class Canvas;
+class Rect;
+}
+
+class SkCanvas;
+
+namespace ui {
+
+// A class to hide the complexity behind setting up a recording into an
+// SkPicture. This is meant to be short-lived within the scope of recording
+// taking place, the SkPicture should be removed from the PaintRecorder once
+// recording is complete and can be cached.
+class COMPOSITOR_EXPORT PaintRecorder {
+ public:
+  // The |recording_bounds| are in the space of the ui::Layer that the
+  // recording is being done in.
+  PaintRecorder(const gfx::Rect& recording_bounds, float device_scale_factor);
+  ~PaintRecorder();
+
+  // Gets the SkCanvas for the recording. Any operations done on this canvas
+  // will be saved in the resulting SkPicture.
+  SkCanvas* skcanvas() { return skcanvas_.get(); }
+
+  // Gets a gfx::Canvas wrapping the SkCanvas for convenience methods.
+  gfx::Canvas* canvas() { return canvas_.get(); }
+
+  // Ends recording and returns the DisplayItem from the object. Any use of the
+  // canvas after calling this would be lost or undefined.
+  scoped_ptr<cc::DrawingDisplayItem> TakeDisplayItem();
+
+  // A helper method for TakeDisplayItem(), when caching the SkPicture is not
+  // required, that inserts it directly into a DisplayItemList.
+  void AppendDisplayItem(cc::DisplayItemList* list);
+
+ private:
+  float device_scale_factor_;
+  SkPictureRecorder recorder_;
+  skia::RefPtr<SkCanvas> skcanvas_;
+  scoped_ptr<gfx::Canvas> canvas_;
+
+  DISALLOW_COPY_AND_ASSIGN(PaintRecorder);
+};
+
+}  // namespace ui
+
+#endif  // UI_COMPOSITOR_PAINT_RECORDER_H_