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();

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

The old code set the target to null here, which matters for the case of the
event already handled. Are you sure we don't need that?

[riajiang, 2017/02/16 19:10:36]

Ah true! I moved it to be inside the case where event hasn't been handled yet.

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