Introduce EventProcessor::OnEventProcessingStarted()

ui/events/event_processor.cc

Index: ui/events/event_processor.cc
diff --git a/ui/events/event_processor.cc b/ui/events/event_processor.cc
index 25c8c3fae92ca2b74e723fce69ee2fe6792b6c49..b508508aa06394c1ca274745fe89aa4f08668058 100644
--- a/ui/events/event_processor.cc
+++ b/ui/events/event_processor.cc
@@ -14,7 +14,6 @@ EventDispatchDetails EventProcessor::OnEventFromSource(Event* event) {
   CHECK(root);
   EventTargeter* targeter = root->GetEventTargeter();
   CHECK(targeter);
-  PrepareEventForDispatch(event);
 
   // If |event| is in the process of being dispatched or has already been
   // dispatched, then dispatch a copy of the event instead.
@@ -26,7 +25,11 @@ EventDispatchDetails EventProcessor::OnEventFromSource(Event* event) {
     event_to_dispatch = event_copy.get();
   }
 
-  EventTarget* target = targeter->FindTargetForEvent(root, event_to_dispatch);
+  OnEventProcessingStarted(event_to_dispatch);
+  EventTarget* target = NULL;
+  if (!event_to_dispatch->handled())
+    target = targeter->FindTargetForEvent(root, event_to_dispatch);

[tdanderson, 2014/09/23 21:30:27]

Another option would be to have EventTargeter::FindTargetForEvent() and all of
its overrides just do an early return NULL if the event is handled, then we
could remove the check at line 30. But I think if you prefer that option, it
should be done in a separate CL.

[sadrul, 2014/09/25 16:12:00]

I think we should do this here, and not require all targeters to have to look at
the event's dispatch state.

[tdanderson, 2014/09/25 17:11:58]

Sounds good, left as-is then.

+
   EventDispatchDetails details;
   while (target) {
     details = DispatchEvent(target, event_to_dispatch);
@@ -51,7 +54,7 @@ EventDispatchDetails EventProcessor::OnEventFromSource(Event* event) {
   return details;
 }
 
-void EventProcessor::PrepareEventForDispatch(Event* event) {
+void EventProcessor::OnEventProcessingStarted(Event* event) {
 }
 
 void EventProcessor::OnEventProcessingFinished(Event* event) {