Handle mac trackpad zoom via GesturePinch events

content/browser/renderer_host/render_widget_host_delegate.h

Index: content/browser/renderer_host/render_widget_host_delegate.h
diff --git a/content/browser/renderer_host/render_widget_host_delegate.h b/content/browser/renderer_host/render_widget_host_delegate.h
index e31975cb20366ee1b6026e7fa6929bbfbefde3c3..983f2824cd8a7a53f38c73ab734a59679843fe33 100644
--- a/content/browser/renderer_host/render_widget_host_delegate.h
+++ b/content/browser/renderer_host/render_widget_host_delegate.h
@@ -52,6 +52,10 @@ class CONTENT_EXPORT RenderWidgetHostDelegate {
   // Returns true if the |event| was handled.
   virtual bool PreHandleGestureEvent(const blink::WebGestureEvent& event);
 
+  // Callback to inform the browser that the renderer did not process the
+  // specified gesture event.  Returns true if the |event| was handled.
+  virtual bool HandleGestureEvent(const blink::WebGestureEvent& event);
+
   // Notifies that screen rects were sent to renderer process.
   virtual void DidSendScreenRects(RenderWidgetHostImpl* rwh) {}