Change event routers from singletons to being owned by the ExtensionService.

chrome/browser/extensions/extension_management_api.h

Index: chrome/browser/extensions/extension_management_api.h
diff --git a/chrome/browser/extensions/extension_management_api.h b/chrome/browser/extensions/extension_management_api.h
index f7a75e599351c368f80c9ef9cd415d6b66773980..65b57d3be7b97d22982f4b9b4f4c3140a892afaf 100644
--- a/chrome/browser/extensions/extension_management_api.h
+++ b/chrome/browser/extensions/extension_management_api.h
@@ -6,7 +6,6 @@
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_MANAGEMENT_API_H__
 #pragma once
 
-#include "base/memory/singleton.h"
 #include "chrome/browser/extensions/extension_function.h"
 #include "content/common/notification_observer.h"
 #include "content/common/notification_registrar.h"
@@ -50,18 +49,12 @@ class UninstallFunction : public ExtensionManagementFunction {
 
 class ExtensionManagementEventRouter : public NotificationObserver {
  public:
-  // Get the singleton instance of the event router.
-  static ExtensionManagementEventRouter* GetInstance();
+  explicit ExtensionManagementEventRouter();
+  virtual ~ExtensionManagementEventRouter();
 
-  // Performs one-time initialization of our singleton.
   void Init();
 
  private:
-  friend struct DefaultSingletonTraits<ExtensionManagementEventRouter>;
-
-  ExtensionManagementEventRouter();
-  virtual ~ExtensionManagementEventRouter();
-
   // NotificationObserver implementation.
   virtual void Observe(NotificationType type,
                        const NotificationSource& source,