Handle mac trackpad zoom via GesturePinch events

content/browser/renderer_host/input/input_router_impl.cc

Index: content/browser/renderer_host/input/input_router_impl.cc
diff --git a/content/browser/renderer_host/input/input_router_impl.cc b/content/browser/renderer_host/input/input_router_impl.cc
index 105051105bb1a7f5bff2551a063bec41ba313a65..9cc5ed0d46e02f2cb9423fe460d225f6d3f52779 100644
--- a/content/browser/renderer_host/input/input_router_impl.cc
+++ b/content/browser/renderer_host/input/input_router_impl.cc
@@ -242,6 +242,7 @@ void InputRouterImpl::SendGestureEvent(
     const GestureEventWithLatencyInfo& original_gesture_event) {
   event_stream_validator_.OnEvent(original_gesture_event.event);
   GestureEventWithLatencyInfo gesture_event(original_gesture_event);
+
   if (touch_action_filter_.FilterGestureEvent(&gesture_event.event))
     return;
 
@@ -419,6 +420,18 @@ void InputRouterImpl::FilterAndSendWebInputEvent(
 void InputRouterImpl::OfferToHandlers(const WebInputEvent& input_event,
                                       const ui::LatencyInfo& latency_info,
                                       bool is_keyboard_shortcut) {
+  // Trackpad pinch gestures are not yet handled by the renderer.

[jdduke (slow), 2014/03/27 02:08:02]

Is that true? The compositor currently doesn't distinguish between source types
when dispatching GesturePinchUpdate
(https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/i...).
 However, maybe that's simply because we don't have any platforms (yet) that
provide such gestures via the trackpad?

As long as this is the behavior we want on *all* platforms, the router is
probably as good as any place for this.

+  // TODO(rbyers): Send mousewheel for trackpad pinch - crbug.com/289887.
+  if (input_event.type == WebInputEvent::GesturePinchUpdate &&
+      static_cast<const WebGestureEvent&>(input_event).sourceDevice ==
+          WebGestureEvent::Touchpad) {
+    ProcessInputEventAck(input_event.type,
+                         INPUT_EVENT_ACK_STATE_NOT_CONSUMED,
+                         latency_info,
+                         ACK_SOURCE_NONE);
+    return;
+  }
+
   if (OfferToOverscrollController(input_event, latency_info))
     return;