mac: Only let two-finger-scrolling trigger history if web doesn't swallow gesture

content/browser/renderer_host/test_render_view_host.h

Index: content/browser/renderer_host/test_render_view_host.h
diff --git a/content/browser/renderer_host/test_render_view_host.h b/content/browser/renderer_host/test_render_view_host.h
index 1c58db99ede877308c1c6463b3f5a70c737f1a7a..6a3841e0d00d6ae8df2f13fc8c7e52940e62c172 100644
--- a/content/browser/renderer_host/test_render_view_host.h
+++ b/content/browser/renderer_host/test_render_view_host.h
@@ -124,6 +124,12 @@ class TestRenderWidgetHostView : public RenderWidgetHostView {
   virtual void ShowCompositorHostWindow(bool show) OVERRIDE;
 #endif
   virtual void SetVisuallyDeemphasized(const SkColor* color, bool animate) { }
+  virtual void UnhandledWheelEvent(
+      const WebKit::WebMouseWheelEvent& event) { }
+  virtual void SetHasHorizontalScrollbar(
+      bool has_horizontal_scrollbar) { }
+  virtual void SetScrollOffsetPinning(
+      bool is_pinned_to_left, bool is_pinned_to_right) { }
 
 #if defined(TOUCH_UI)
   virtual void AcceleratedSurfaceSetIOSurface(