Support chrome.windows extension API events for browserless Panels.

chrome/browser/extensions/window_controller_list.h

Index: chrome/browser/extensions/window_controller_list.h
diff --git a/chrome/browser/extensions/window_controller_list.h b/chrome/browser/extensions/window_controller_list.h
index 3c6915b036739b54346f90d1358ebf9cae407fe8..a32baf6a31218b667646aed2795413103cd9e52d 100644
--- a/chrome/browser/extensions/window_controller_list.h
+++ b/chrome/browser/extensions/window_controller_list.h
@@ -9,6 +9,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/memory/singleton.h"
+#include "base/observer_list.h"
 #include "chrome/browser/extensions/window_controller.h"
 
 class Profile;
@@ -16,6 +17,8 @@ class UIThreadExtensionFunction;
 
 namespace extensions {
 
+class WindowControllerListObserver;
+
 // Class to maintain a list of WindowControllers.
 class WindowControllerList {
  public:
@@ -27,6 +30,9 @@ class WindowControllerList {
   void AddExtensionWindow(WindowController* window);
   void RemoveExtensionWindow(WindowController* window);
 
+  void AddObserver(WindowControllerListObserver* observer);
+  void RemoveObserver(WindowControllerListObserver* observer);
+
   // Returns a window matching the context the function was invoked in.
   WindowController* FindWindowForFunctionById(
       const UIThreadExtensionFunction* function,
@@ -47,6 +53,8 @@ class WindowControllerList {
   // Entries are not owned by this class and must be removed when destroyed.
   ControllerList windows_;
 
+  ObserverList<WindowControllerListObserver> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowControllerList);
 };