Enable pinch-zoom telemetry on Mac

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 252250ec3781eb1d579b3ca550e1c8182145556f..23b8eecef6dfbc770b242c250ca2ea91d03edeaf 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -41,6 +41,7 @@
 #include "content/browser/renderer_host/render_widget_helper.h"
 #include "content/browser/renderer_host/render_widget_host_delegate.h"
 #include "content/browser/renderer_host/render_widget_host_input_event_router.h"
+#import "content/browser/renderer_host/input/synthetic_gesture_target_mac.h"
 #import "content/browser/renderer_host/render_widget_host_view_mac_dictionary_helper.h"
 #import "content/browser/renderer_host/render_widget_host_view_mac_editcommand_helper.h"
 #include "content/browser/renderer_host/render_widget_resize_helper_mac.h"
@@ -1637,6 +1638,14 @@ void RenderWidgetHostViewMac::WheelEventAck(
     [cocoa_view_ processedWheelEvent:event consumed:consumed];
 }
 
+scoped_ptr<SyntheticGestureTarget>
+RenderWidgetHostViewMac::CreateSyntheticGestureTarget() {
+  RenderWidgetHostImpl* host =
+      RenderWidgetHostImpl::From(GetRenderWidgetHost());
+  return scoped_ptr<SyntheticGestureTarget>(
+      new SyntheticGestureTargetMac(host, cocoa_view_));
+}
+
 uint32_t RenderWidgetHostViewMac::GetSurfaceIdNamespace() {
   if (delegated_frame_host_)
     return delegated_frame_host_->GetSurfaceIdNamespace();