Avoid two targeting phases in aura client-lib and EventProcessor.

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 61d2e72138a8dc51beb04f960b19197d715c750d..18f3a5577f35ea8982cbcb35914b4f166953b9a0 100644
--- a/ui/events/event_processor.cc
+++ b/ui/events/event_processor.cc
@@ -10,11 +10,6 @@
 namespace ui {
 
 EventDispatchDetails EventProcessor::OnEventFromSource(Event* event) {
-  EventTarget* root = GetRootTarget();
-  CHECK(root);
-  EventTargeter* targeter = root->GetEventTargeter();
-  CHECK(targeter);
-
   // If |event| is in the process of being dispatched or has already been
   // dispatched, then dispatch a copy of the event instead.
   bool dispatch_original_event = event->phase() == EP_PREDISPATCH;
@@ -26,9 +21,17 @@ EventDispatchDetails EventProcessor::OnEventFromSource(Event* event) {
   }
 
   OnEventProcessingStarted(event_to_dispatch);
-  EventTarget* target = NULL;
-  if (!event_to_dispatch->handled())
+  EventTarget* target = nullptr;
+  EventTargeter* targeter = nullptr;
+  if (!event_to_dispatch->handled()) {
+    EventTarget* root = GetRootForEvent(event_to_dispatch);
+    DCHECK(root);
+    targeter = root->GetEventTargeter();
+    if (!targeter)
+      targeter = GetDefaultEventTargeter();
+    DCHECK(targeter);
     target = targeter->FindTargetForEvent(root, event_to_dispatch);

[sadrul, 2017/02/14 21:40:10]

Hm. This means we are always using the local targeter. But this is not what we
want, right? When mus gives us a target, and none of the ancestor has a
targeter, we should just use that target.

[riajiang, 2017/02/15 18:09:27]

Makes sense. I added one more check to see if there was an event target set,
we'll use that target if there was no targeter but a target?

+  }
 
   EventDispatchDetails details;
   while (target) {