Get event targetting working for mouse events.

ui/events/event_target_iterator.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_EVENTS_EVENT_TARGET_ITERATOR_H_
 #define UI_EVENTS_EVENT_TARGET_ITERATOR_H_
 
 #include <vector>
 
 namespace ui {
@@ skipping 10 matching lines @@
 // Provides an EventTargetIterator implementation for iterating over a list of
 // EventTargets. The list is iterated in the reverse order, since typically the
 // EventTargets are maintained in increasing z-order in the lists.
 template<typename T>
 class EventTargetIteratorImpl : public EventTargetIterator {
  public:
   explicit EventTargetIteratorImpl(const std::vector<T*>& children)
       : begin_(children.rbegin()),
         end_(children.rend()) {
   }
-  virtual ~EventTargetIteratorImpl() {}
+  ~EventTargetIteratorImpl() override {}
 
-  virtual EventTarget* GetNextTarget() override {
+  EventTarget* GetNextTarget() override {
     if (begin_ == end_)
-      return NULL;
+      return nullptr;
     EventTarget* target = *(begin_);
     ++begin_;
     return target;
   }
 
  private:
   typename std::vector<T*>::const_reverse_iterator begin_;
   typename std::vector<T*>::const_reverse_iterator end_;
 };
 
+// Provides a version which keeps a copy of the data (for when it has to be
+// derived instead of pointed at).
+template <typename T>
+class CopyingEventTargetIteratorImpl : public EventTargetIterator {
+ public:
+  explicit CopyingEventTargetIteratorImpl(const std::vector<T*>& children)
+      : children_(children),
+        begin_(children_.rbegin()),
+        end_(children_.rend()) {}
+  ~CopyingEventTargetIteratorImpl() override {}
+
+  EventTarget* GetNextTarget() override {
+    if (begin_ == end_)
+      return nullptr;
+    EventTarget* target = *(begin_);
+    ++begin_;
+    return target;
+  }
+
+ private:
+  typename std::vector<T*> children_;
+  typename std::vector<T*>::const_reverse_iterator begin_;
+  typename std::vector<T*>::const_reverse_iterator end_;
+};
+
 }  // namespace ui
 
 #endif  // UI_EVENTS_EVENT_TARGET_ITERATOR_H_