Synthesize ctrl-wheel events on touchpad pinch

content/browser/renderer_host/input/input_router_impl.h

Index: content/browser/renderer_host/input/input_router_impl.h
diff --git a/content/browser/renderer_host/input/input_router_impl.h b/content/browser/renderer_host/input/input_router_impl.h
index 8c512348a6bcf93988e02c4bf627d8055f9ce7fe..a586d5d339e382396f40cd49b5b7e5d491d0e1dd 100644
--- a/content/browser/renderer_host/input/input_router_impl.h
+++ b/content/browser/renderer_host/input/input_router_impl.h
@@ -118,6 +118,26 @@ private:
                        const ui::LatencyInfo& latency_info,
                        bool is_keyboard_shortcut);
 
+  // A data structure that attaches some metadata to a WebMouseWheelEvent
+  // and its latency info.
+  struct QueuedWheelEvent {
+    QueuedWheelEvent();
+    QueuedWheelEvent(const MouseWheelEventWithLatencyInfo& event,
+                     bool synthesized_from_pinch);
+    ~QueuedWheelEvent();
+
+    MouseWheelEventWithLatencyInfo event;
+    bool synthesized_from_pinch;
+  };
+
+  // Enqueue or send a mouse wheel event.
+  void SendWheelEvent(const QueuedWheelEvent& wheel_event);
+
+  // Given a Touchpad GesturePinchUpdate event, create and send a synthetic
+  // wheel event for it.
+  void SendSyntheticWheelEventForPinch(
+      const GestureEventWithLatencyInfo& pinch_event);
+
   // IPC message handlers
   void OnInputEventAck(blink::WebInputEvent::Type event_type,
                        InputEventAckState ack_result,
@@ -216,7 +236,7 @@ private:
   // (Similar to |mouse_move_pending_|.) True if a mouse wheel event was sent
   // and we are waiting for a corresponding ack.
   bool mouse_wheel_pending_;
-  MouseWheelEventWithLatencyInfo current_wheel_event_;
+  QueuedWheelEvent current_wheel_event_;
 
   // (Similar to |next_mouse_move_|.) The next mouse wheel events to send.
   // Unlike mouse moves, mouse wheel events received while one is pending are
@@ -225,7 +245,7 @@ private:
   // high rate; not waiting for the ack results in jankiness, and using the same
   // mechanism as for mouse moves (just dropping old events when multiple ones
   // would be queued) results in very slow scrolling.
-  typedef std::deque<MouseWheelEventWithLatencyInfo> WheelEventQueue;
+  typedef std::deque<QueuedWheelEvent> WheelEventQueue;
   WheelEventQueue coalesced_mouse_wheel_events_;
 
   // A queue of keyboard events. We can't trust data from the renderer so we