Refactor GestureNavigation to eliminate code redundancy

content/browser/web_contents/aura/overscroll_navigation_overlay.h

Index: content/browser/web_contents/aura/overscroll_navigation_overlay.h
diff --git a/content/browser/web_contents/aura/overscroll_navigation_overlay.h b/content/browser/web_contents/aura/overscroll_navigation_overlay.h
index db9871c024981ff908b20bfd9b2ed1baddcc6eaa..5ff57afc7daacaeb462674dacc1d2a88d2d892f0 100644
--- a/content/browser/web_contents/aura/overscroll_navigation_overlay.h
+++ b/content/browser/web_contents/aura/overscroll_navigation_overlay.h
@@ -8,8 +8,10 @@
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "content/browser/web_contents/aura/window_slider.h"
+#include "content/browser/web_contents/web_contents_view_aura.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/web_contents_observer.h"
+#include "ui/gfx/image/image.h"
 
 struct ViewHostMsg_UpdateRect_Params;
 
@@ -31,7 +33,11 @@ class CONTENT_EXPORT OverscrollNavigationOverlay
     : public WebContentsObserver,
       public WindowSlider::Delegate {
  public:
-  explicit OverscrollNavigationOverlay(WebContentsImpl* web_contents);
+  // TODO move this somewhere else.
+  enum Direction { FORWARD, BACKWARD, NONE };
+
+  explicit OverscrollNavigationOverlay(WebContentsImpl* web_contents,
+                                       WebContentsViewAura* wcva);
   ~OverscrollNavigationOverlay() override;
 
   bool has_window() const { return !!window_.get(); }
@@ -51,6 +57,14 @@ class CONTENT_EXPORT OverscrollNavigationOverlay
   void SetOverlayWindow(scoped_ptr<aura::Window> window,
                         aura_extra::ImageWindowDelegate* delegate);
 
+  const gfx::Image GetImageForDirection(Direction direction);
+
+  // Creates a layer with a screenshot for a given direction.
+  scoped_ptr<ui::Layer> CreateLayerForDirection(Direction direction);
+
+  Direction GetNavigationDirection(const NavigationController& controller,
+                                   OverscrollMode mode);
+
  private:
   friend class OverscrollNavigationOverlayTest;
   FRIEND_TEST_ALL_PREFIXES(OverscrollNavigationOverlayTest,
@@ -123,6 +137,9 @@ class CONTENT_EXPORT OverscrollNavigationOverlay
   // The LayerDelegate used for the back/front layers during a slide.
   scoped_ptr<ImageLayerDelegate> layer_delegate_;
 
+  // TODO use a delegate.
+  WebContentsViewAura* wcva_;
+
   DISALLOW_COPY_AND_ASSIGN(OverscrollNavigationOverlay);
 };