Moves transient window observer methods out of WindowObserver

ui/views/corewm/transient_window_manager.h

Index: ui/views/corewm/transient_window_manager.h
diff --git a/ui/views/corewm/transient_window_manager.h b/ui/views/corewm/transient_window_manager.h
index 72c9f998d663d5dad178780f329b62abb3bef1de..93404ddb37295e306a11e3f2f7c1379d08f5da35 100644
--- a/ui/views/corewm/transient_window_manager.h
+++ b/ui/views/corewm/transient_window_manager.h
@@ -7,12 +7,15 @@
 
 #include <vector>
 
+#include "base/observer_list.h"
 #include "ui/aura/window_observer.h"
 #include "ui/views/views_export.h"
 
 namespace views {
 namespace corewm {
 
+class TransientWindowObserver;
+
 // TransientWindowManager manages the set of transient children for a window
 // along with the transient parent. Transient children get the following
 // behavior:
@@ -37,6 +40,9 @@ class VIEWS_EXPORT TransientWindowManager : public aura::WindowObserver {
   // WARNING: this may return NULL.
   static const TransientWindowManager* Get(const aura::Window* window);
 
+  void AddObserver(TransientWindowObserver* observer);
+  void RemoveObserver(TransientWindowObserver* observer);
+
   // Adds or removes a transient child.
   void AddTransientChild(aura::Window* child);
   void RemoveTransientChild(aura::Window* child);
@@ -87,6 +93,8 @@ class VIEWS_EXPORT TransientWindowManager : public aura::WindowObserver {
   // transient ancestor changing. This is a pointer to a value on the stack.
   StackingPair* stacking_pair_;
 
+  ObserverList<TransientWindowObserver> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(TransientWindowManager);
 };