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..b50e49ffb26405d0cfbb17bffad54b68a600a0aa
--- /dev/null
+++ b/content/browser/web_contents/aura/overscroll_window_animation.h
@@ -0,0 +1,113 @@
+// 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 "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 OverscrollLayerWrapper;
+class ShadowLayerDelegate;
+
+// Manages the animations during an overscroll navigation by handling overscroll
+// events.
+class CONTENT_EXPORT OverscrollWindowAnimation
+    : public OverscrollControllerDelegate,
+      ui::ImplicitAnimationObserver {
+ public:
+  enum Direction { FORWARD, BACKWARD, NONE };

[mfomitchev, 2015/03/05 23:37:06]

In WindowSlider Direction was  SLIDE_UNKNOWN, SLIDE_BACK, SLIDE_FRONT. Note that
BACK/FRONT means BEHIND/IN FRONT, not BACKWARDS/FORWARD. I think we should
either use the same semantics or perhaps LEFT/RIGHT. BACKWARDS/FORWARD doesn't
really make sense here - it only makes sense in the context of browser history
navigation, but OWA shouldn't be tied to that necessarily.

[Nina, 2015/03/09 15:54:53]

In this case, FORWARD == FRONT and BACKWARD == BACK. I found using the FRONT and
BACK, as in the where the layer is stacked, was not intuitive for ONO, and I
especially wanted to avoid having two different enums for the direction.

However, due to the fact that we know have two callbacks for
Create*LayerWrapper, having two enums make more sense. See how you find the new
implementation.

+
+  // Delegate class that interfaces with the window animation, responsible for
+  // navigation.
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // The following two functions create a layer wrapper and transfer back its
+    // ownership.
+    virtual scoped_ptr<OverscrollLayerWrapper> CreateFrontLayer() = 0;
+    virtual scoped_ptr<OverscrollLayerWrapper> CreateBackLayer() = 0;
+
+    // Called when the animation has been completed. The delagate can then
+    // dismiss the overlay layer, or wait for the page to load first.

[mfomitchev, 2015/03/06 01:36:43]

We shouldn't reference page load in OWA's comments. OWA shouldn't know anything
about page load and navigation. It is just moving windows/layers around.

[Nina, 2015/03/09 15:54:53]

Done.

+    virtual void OnOverscrollCompleted(

[mfomitchev, 2015/03/05 23:37:06]

Don't fire Completed() on failures - add another method for failure like
WindowSlider.Delegate::XYZReset().

[Nina, 2015/03/09 15:54:53]

Done.

+        scoped_ptr<OverscrollLayerWrapper> layer_wrapper) = 0;
+
+    // Called when we know the animation is going to complete. This should start
+    // the navigation.
+    virtual void OnOverscrollCompleting() = 0;

[mfomitchev, 2015/03/06 01:36:43]

Completing() should be declared before Completed() IMO

[Nina, 2015/03/09 15:54:53]

Done.

+  };
+
+  OverscrollWindowAnimation();
+
+  ~OverscrollWindowAnimation() override;
+
+  // Returns true if we are currently handling a slide animation.
+  bool is_active() const { return !!layer_wrapper_; }
+
+  void set_delegate(Delegate* delegate) { delegate_ = delegate; }
+
+  void set_live_window(aura::Window* live_window) {
+    live_window_ = live_window;

[mfomitchev, 2015/03/05 23:37:06]

DCHECK(live_window)

[Nina, 2015/03/09 15:54:53]

Done.

+  }
+
+  // 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,
+                              OverscrollMode new_mode) override;
+
+ private:
+  // Starts the overscroll cancelled animation.
+  void CancelOverscroll();
+
+  // 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 overscroll gesture.
+  ui::Layer* GetAnimatedLayer();
+
+  // ui::ImplicitAnimationObserver:
+  void OnImplicitAnimationsCompleted() override;
+
+  // Wrapper that owns the overscroll window.
+  scoped_ptr<OverscrollLayerWrapper> layer_wrapper_;
+
+  // Shadow shown under the animated layer.
+  scoped_ptr<ShadowLayerDelegate> shadow_;
+
+  // Live window holding the currently active web contents.

[mfomitchev, 2015/03/05 23:37:06]

not web contents for slider case

[Nina, 2015/03/09 15:54:53]

Done.

+  aura::Window* live_window_;
+
+  // Delegate that provides the animation target and handles navigation.
+  Delegate* delegate_;
+
+  // The current overscroll direction.
+  Direction direction_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_WINDOW_ANIMATION_H_