Introduce EventProcessor::OnEventProcessingStarted()

ui/events/test/test_event_processor.h

Index: ui/events/test/test_event_processor.h
diff --git a/ui/events/test/test_event_processor.h b/ui/events/test/test_event_processor.h
index 5d4d98a6d59c878a09104f35e9481ab966e456cf..4ac07b952f499b3a33020ccea73bd42e901a62c3 100644
--- a/ui/events/test/test_event_processor.h
+++ b/ui/events/test/test_event_processor.h
@@ -16,22 +16,35 @@ class TestEventProcessor : public EventProcessor {
   TestEventProcessor();
   virtual ~TestEventProcessor();
 
+  int num_times_processing_started() const {
+    return num_times_processing_started_;
+  }
+
   int num_times_processing_finished() const {
     return num_times_processing_finished_;
   }
 
   void SetRoot(scoped_ptr<EventTarget> root);
-  void ResetCounts();
+  void SetShouldProcessingOccur(bool occur);
+  void Reset();
 
   // EventProcessor:
   virtual bool CanDispatchToTarget(EventTarget* target) OVERRIDE;
   virtual EventTarget* GetRootTarget() OVERRIDE;
   virtual EventDispatchDetails OnEventFromSource(Event* event) OVERRIDE;
+  virtual void OnEventProcessingStarted(Event* event) OVERRIDE;
   virtual void OnEventProcessingFinished(Event* event) OVERRIDE;
 
  private:
   scoped_ptr<EventTarget> root_;
 
+  // Used in our override of OnEventProcessingStarted(). If this value is
+  // false, mark incoming events as handled.
+  bool should_processing_occur_;
+
+  // Counts the number of times OnEventProcessingStarted() has been called.
+  int num_times_processing_started_;
+
   // Counts the number of times OnEventProcessingFinished() has been called.
   int num_times_processing_finished_;