Handle mac trackpad zoom via GesturePinch events

content/browser/renderer_host/render_widget_host_delegate.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/renderer_host/render_widget_host_delegate.h"
 
 namespace content {
 
 bool RenderWidgetHostDelegate::PreHandleKeyboardEvent(
     const NativeWebKeyboardEvent& event,
     bool* is_keyboard_shortcut) {
   return false;
 }
 
 bool RenderWidgetHostDelegate::HandleWheelEvent(
     const blink::WebMouseWheelEvent& event) {
   return false;
 }
 
 bool RenderWidgetHostDelegate::PreHandleGestureEvent(
     const blink::WebGestureEvent& event) {
   return false;
 }
 
+bool RenderWidgetHostDelegate::HandleGestureEvent(
+    const blink::WebGestureEvent& event) {
+  return false;
+}
+
 #if defined(OS_WIN)
 gfx::NativeViewAccessible
 RenderWidgetHostDelegate::GetParentNativeViewAccessible() {
   return NULL;
 }
 #endif
 
 }  // namespace content