Introduce ui::PaintRecorder and use it for CursorWindowDelegate.

ui/compositor/paint_recorder.cc

+// 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.
+
+#include "ui/compositor/paint_recorder.h"
+
+#include "cc/resources/display_item_list.h"
+#include "cc/resources/drawing_display_item.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/skia_util.h"
+
+namespace ui {
+
+PaintRecorder::PaintRecorder(const gfx::Rect& recording_bounds,
+                             float device_scale_factor)
+    : device_scale_factor_(device_scale_factor) {
+  SkRTreeFactory* no_factory = nullptr;
+  skcanvas_ = skia::SharePtr(recorder_.beginRecording(
+      gfx::RectToSkRect(recording_bounds), no_factory,
+      SkPictureRecorder::kComputeSaveLayerInfo_RecordFlag));
+  skcanvas_->clipRect(gfx::RectToSkRect(recording_bounds));
+  canvas_ = make_scoped_ptr(gfx::Canvas::CreateCanvasWithoutScaling(
+      skcanvas(), device_scale_factor_));
+}
+
+PaintRecorder::~PaintRecorder() {
+}
+
+scoped_ptr<cc::DrawingDisplayItem> PaintRecorder::TakeDisplayItem() {
+  DCHECK(skcanvas_);
+  scoped_ptr<cc::DrawingDisplayItem> item =
+      cc::DrawingDisplayItem::Create(skia::AdoptRef(recorder_.endRecording()));
+  skcanvas_.clear();  // Prevent this method from being called again.
+  return item;
+}
+
+void PaintRecorder::AppendDisplayItem(cc::DisplayItemList* list) {
+  DCHECK(skcanvas_);
+  list->AppendItem(TakeDisplayItem());
+}
+
+}  // namespace ui