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..f80cb91b6404cd377b6fa40cb9cd35d1c4177a9c 100644
--- a/ui/events/event_processor.cc
+++ b/ui/events/event_processor.cc
@@ -10,14 +10,11 @@
 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.
+  // dispatched, then dispatch a copy of the event instead. We expect event
+  // target to be already set if event phase is after EP_PREDISPATCH.
   bool dispatch_original_event = event->phase() == EP_PREDISPATCH;
+  DCHECK(dispatch_original_event || event->target());
   Event* event_to_dispatch = event;
   std::unique_ptr<Event> event_copy;
   if (!dispatch_original_event) {
@@ -26,9 +23,23 @@ EventDispatchDetails EventProcessor::OnEventFromSource(Event* event) {
   }
 
   OnEventProcessingStarted(event_to_dispatch);
-  EventTarget* target = NULL;
-  if (!event_to_dispatch->handled())
-    target = targeter->FindTargetForEvent(root, event_to_dispatch);
+  EventTarget* target = nullptr;
+  EventTargeter* targeter = nullptr;
+  if (!event_to_dispatch->handled()) {
+    EventTarget* root = GetRootForEvent(event_to_dispatch);
+    DCHECK(root);
+    targeter = root->GetEventTargeter();
+    if (targeter) {
+      target = targeter->FindTargetForEvent(root, event_to_dispatch);
+    } else {
+      targeter = GetDefaultEventTargeter();
+      if (event_to_dispatch->target())
+        target = root;
+      else
+        target = targeter->FindTargetForEvent(root, event_to_dispatch);
+    }
+    DCHECK(targeter);
+  }
 
   EventDispatchDetails details;
   while (target) {