Refactor GestureNavigation to eliminate code redundancy

content/browser/web_contents/aura/overscroll_layer_wrapper.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 CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_LAYER_WRAPPER_H_
+#define CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_LAYER_WRAPPER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "ui/aura/window.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/image/image.h"
+#include "ui/gfx/transform.h"
+
+namespace ui {
+class Layer;
+class LayerAnimator;
+}
+
+namespace content {
+
+class ImageLayerDelegate;
+class ShadowLayerDelegate;
+
+// Wraps a window or a layer, exposing some of their common API to allow
+// overscroll animations for both cases. If wrapping a layer, assumes its
+// ownership.
+class OverscrollLayerWrapper {
+ public:
+  // Takes a pointer to the |window|.
+  explicit OverscrollLayerWrapper(scoped_ptr<aura::Window> window);
+
+  // Assumes ownership of the |layer|.
+  explicit OverscrollLayerWrapper(scoped_ptr<ui::Layer> layer);
+
+  ~OverscrollLayerWrapper();
+
+  // Returns the wrapped |layer_| or the |window_| layer.
+  ui::Layer* layer() { return layer_ ? layer_.get() : window_->layer(); }
+
+  // Returns true if a window is being wrapped.
+  bool has_window() { return !!window_; }
+
+  // Transfers ownership of the wrapped |layer_|.
+  scoped_ptr<ui::Layer> AcquireLayer();
+
+  // Transfers ownership of the wrapped |window_|.
+  scoped_ptr<aura::Window> AcquireWindow();
+
+  // Returns the wrapped target layer bounds.
+  gfx::Rect GetBounds();
+
+ private:
+  // The wrapped layer.
+  scoped_ptr<ui::Layer> layer_;
+
+  // The wrapped window.
+  scoped_ptr<aura::Window> window_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_LAYER_WRAPPER_H_