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

content/browser/renderer_host/render_widget_host_view.h

Index: content/browser/renderer_host/render_widget_host_view.h
diff --git a/content/browser/renderer_host/render_widget_host_view.h b/content/browser/renderer_host/render_widget_host_view.h
index cd1bc2f95490d91957d9c4ea293cdda165ef0be7..bffd5206e7ba3d37e603df1252ba2445a59e674a 100644
--- a/content/browser/renderer_host/render_widget_host_view.h
+++ b/content/browser/renderer_host/render_widget_host_view.h
@@ -16,6 +16,7 @@
 #include "base/process_util.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkColor.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPopupType.h"
 #include "ui/base/ime/text_input_type.h"
 #include "ui/base/range/range.h"
@@ -296,6 +297,12 @@ class RenderWidgetHostView {
   // ignored.
   virtual void SetVisuallyDeemphasized(const SkColor* color, bool animate) = 0;
 
+  virtual void UnhandledWheelEvent(const WebKit::WebMouseWheelEvent& event) = 0;
+
+  virtual void SetHasHorizontalScrollbar(bool has_horizontal_scrollbar) = 0;
+  virtual void SetScrollOffsetPinning(
+      bool is_pinned_to_left, bool is_pinned_to_right) = 0;
+
   void set_popup_type(WebKit::WebPopupType popup_type) {
     popup_type_ = popup_type;
   }