Refactor GestureNavigation to eliminate code redundancy

content/browser/web_contents/aura/overscroll_window_animation.h

Index: content/browser/web_contents/aura/overscroll_window_animation.h
diff --git a/content/browser/web_contents/aura/overscroll_window_animation.h b/content/browser/web_contents/aura/overscroll_window_animation.h
new file mode 100644
index 0000000000000000000000000000000000000000..79a37c1a0dd6d9c9b55443b074e38709111cc9de
--- /dev/null
+++ b/content/browser/web_contents/aura/overscroll_window_animation.h
@@ -0,0 +1,123 @@
+// 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_WINDOW_ANIMATION_H_
+#define CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_WINDOW_ANIMATION_H_
+
+#include "base/gtest_prod_util.h"
+#include "content/browser/renderer_host/overscroll_controller_delegate.h"
+#include "content/common/content_export.h"
+#include "ui/compositor/layer_animation_observer.h"
+
+namespace aura {
+class Window;
+}
+
+namespace ui {
+class Layer;
+class LayerAnimator;
+}
+
+namespace content {
+
+class ShadowLayerDelegate;
+class WebContentsImpl;
+
+// Manages the animation of a window sliding on top or behind another one. The
+// main window, which is the one displayed before the animation starts, is not
+// owned by OverscrollWindowAnimation, while the slide window, created at the
+// start of the animation, is owned by us for its duration.
+class CONTENT_EXPORT OverscrollWindowAnimation
+    : public OverscrollControllerDelegate,
+      ui::ImplicitAnimationObserver {
+ public:
+  // The direction of this animation. SLIDE_FRONT indicates that the main window
+  // stays behind while the slide window one moves in from the right. SLIDE_BACK

[mfomitchev, 2015/03/31 21:04:07]

stays still, while the slide window moves on top of it, entering from the right.

[Nina, 2015/04/01 18:10:01]

Done.

+  // means that the main window is animated to the right, revealing the slide
+  // window on the back. SLIDE_NONE means we are not animating yet. Left and

[mfomitchev, 2015/03/31 21:04:07]

in the back, which stays still.

[Nina, 2015/04/01 18:10:01]

Done.

+  // right are reversed for users of RTL languages, but stack order remains

[mfomitchev, 2015/03/31 21:04:08]

Directions are reversed for RTL languages,..

[Nina, 2015/04/01 18:10:01]

Done.

+  // unchanged.
+  enum Direction { SLIDE_FRONT, SLIDE_BACK, SLIDE_NONE };
+
+  // Delegate class that interfaces with the window animation.
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // The following two functions create a slide window and transfer back its
+    // ownership.
+    virtual scoped_ptr<aura::Window> CreateFrontWindow() = 0;
+    virtual scoped_ptr<aura::Window> CreateBackWindow() = 0;
+
+    // Returns the main window that participates in the animation. We do not own
+    // this window.
+    virtual aura::Window* GetMainWindow() const = 0;
+
+    // Called when we know the animation is going to complete successfully, but
+    // before it actually completes.
+    virtual void OnOverscrollCompleting() = 0;
+
+    // Called when the animation has been completed. The slide window's
+    // ownership is transferred.

[mfomitchev, 2015/03/31 21:04:08]

"The slide window's ownership is transferred" -> "|window| points to the slide
window". Ownership is implicit from scoped_ptr.

[Nina, 2015/04/01 18:10:01]

Done.

+    virtual void OnOverscrollCompleted(scoped_ptr<aura::Window> window) = 0;
+
+    // Called when the overscroll gesture has been aborted, after the abort
+    // animation finishes.
+    virtual void OnOverscrollAborted() = 0;
+  };
+
+  explicit OverscrollWindowAnimation(Delegate* delegate);
+
+  ~OverscrollWindowAnimation() override;
+
+  // Returns true if we are currently animating.
+  bool is_active() const { return !!slide_window_; }
+
+  // Overridden from OverscrollControllerDelegate:
+  gfx::Rect GetVisibleBounds() const override;
+
+  bool OnOverscrollUpdate(float delta_x, float delta_y) override;
+
+  void OnOverscrollComplete(OverscrollMode overscroll_mode) override;
+
+  void OnOverscrollModeChange(OverscrollMode old_mode,

[mfomitchev, 2015/03/31 21:04:07]

Leave no space between overridden methods

[Nina, 2015/04/01 18:10:01]

Done.

+                              OverscrollMode new_mode) override;
+
+ private:
+  // Cancels the animation, animating the front window to its original position.
+  void CancelAnimation();
+
+  // Moves the animated window according to the given scroll deltas. Returns
+  // true if the update moved the window.
+  bool UpdateForScroll(float delta_x);
+
+  // Returns a translation on the x axis for the given overscroll.
+  float GetTranslationForOverscroll(float delta_x);
+
+  // Returns the layer that is animated for the animation.
+  ui::Layer* GetFrontLayer() const;
+
+  // ui::ImplicitAnimationObserver:
+  void OnImplicitAnimationsCompleted() override;
+
+  // We own the window created for the animation.
+  scoped_ptr<aura::Window> slide_window_;
+
+  // Shadow shown under the animated layer.
+  scoped_ptr<ShadowLayerDelegate> shadow_;
+
+  // Delegate that provides the animation target and is notified of the
+  // animation state.
+  Delegate* delegate_;
+
+  // The current animation direction.
+  Direction direction_;
+
+  // Indicates if the current animation has been cancelled.

[mfomitchev, 2015/03/31 21:04:07]

Pick either "aborted" or "cancelled and stick to that within this class. Right
now you use both. Also - this is only true while the "abort" animation is
progress? If so - say that.

[Nina, 2015/04/01 18:10:01]

s/abort/cancel for the overscroll related functions.

+  bool overscroll_cancelled_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_WINDOW_ANIMATION_H_