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

ui/events/event_processor.h

Index: ui/events/event_processor.h
diff --git a/ui/events/event_processor.h b/ui/events/event_processor.h
index 8e6305148ba5d5dca5d8f3a1bdb03a6ac5a06038..9ee7c4e0ab3e767c45b1d18b5cddf04723ed9f45 100644
--- a/ui/events/event_processor.h
+++ b/ui/events/event_processor.h
@@ -10,14 +10,19 @@
 
 namespace ui {
 
+class EventTargeter;
+
 // EventProcessor receives an event from an EventSource and dispatches it to a
 // tree of EventTargets.
 class EVENTS_EXPORT EventProcessor : public EventDispatcherDelegate {
  public:
   ~EventProcessor() override {}
 
-  // Returns the root of the tree this event processor owns.
-  virtual EventTarget* GetRootTarget() = 0;
+  // Returns the EventTarget with the right EventTargeter that we should use for
+  // dispatching this |event|.
+  virtual EventTarget* GetRootForEvent(Event* event) = 0;
+
+  virtual EventTargeter* GetDefaultEventTargeter() = 0;

[sadrul, 2017/02/13 17:05:42]

Document, e.g. "If the root target returned by GetRootForEvent() does not have a
targeter set, then the default targeter is used to find the target."

[riajiang, 2017/02/13 23:30:34]

Done.

 
   // Dispatches an event received from the EventSource to the tree of
   // EventTargets (whose root is returned by GetRootTarget()).  The co-ordinate