Add HandleInputEventAck message to allow out-of-process plugins to respond to user gestures.

ppapi/proxy/ppp_input_event_proxy.cc

Index: ppapi/proxy/ppp_input_event_proxy.cc
===================================================================
--- ppapi/proxy/ppp_input_event_proxy.cc	(revision 125463)
+++ ppapi/proxy/ppp_input_event_proxy.cc	(working copy)
@@ -101,6 +101,7 @@
   CallWhileUnlocked(ppp_input_event_impl_->HandleInputEvent,
                     instance,
                     resource->pp_resource());
+  HandleInputEventAck(instance, data.event_time_stamp);
 }
 
 void PPP_InputEvent_Proxy::OnMsgHandleFilteredInputEvent(
@@ -112,7 +113,20 @@
   *result = CallWhileUnlocked(ppp_input_event_impl_->HandleInputEvent,
                               instance,
                               resource->pp_resource());
+  HandleInputEventAck(instance, data.event_time_stamp);
 }
 
+void PPP_InputEvent_Proxy::HandleInputEventAck(
+    PP_Instance instance, PP_TimeTicks timestamp) {
+  PluginDispatcher* dispatcher = PluginDispatcher::GetForInstance(instance);
+  if (dispatcher) {
+    // Note that we're sending the message to the host PPB_InstanceProxy.
+    dispatcher->Send(new PpapiMsg_PPPInputEvent_HandleInputEvent_ACK(
+        API_ID_PPB_INSTANCE, instance, timestamp));
+  } else {
+    NOTREACHED();
+  }
+}
+
 }  // namespace proxy
 }  // namespace ppapi