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..ef7a0f70d93f1ccfb1e8dc01a693884887892387 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 +21,21 @@ 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 = event->target();
+  EventTargeter* targeter = nullptr;
+  if (!event_to_dispatch->handled()) {
+    EventTarget* root = GetRootForEvent(event_to_dispatch);
+    DCHECK(root);
+    targeter = root->GetEventTargeter();
+    if (!targeter) {
+      targeter = GetDefaultEventTargeter();
+      if (!target)
+        target = targeter->FindTargetForEvent(root, event_to_dispatch);
+    } else {
+      target = targeter->FindTargetForEvent(root, event_to_dispatch);

[sky, 2017/02/15 20:47:17]

This duplicates line 33. I think it would be easier if you closed the if started
on line 30 at line 32 and moved the if the starts on line 32 after it, e.g.
if (!targeter)
  targeter = ...
if (!target)
  target = ...

[riajiang, 2017/02/16 00:34:08]

I'm not sure if I understood this. There's a case when we have both target and
targeter (mus-ws sets the target but ash wanted to use that custom targeter), we
do want to update the target using this custom targeter in that case?

[sky, 2017/02/16 01:03:02]

Ah, I see it now. Thanks.

+    }
+    DCHECK(targeter);
+  }
 
   EventDispatchDetails details;
   while (target) {