Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm

Index: chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm
diff --git a/chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm b/chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm
index 91f2fee891bd7819d3ff6f9c11d132b77ed89a43..7748a1dd1ca28319d4d19eb088147342f60f0d0b 100644
--- a/chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm
+++ b/chrome/browser/ui/cocoa/toolbar/toolbar_controller.mm
@@ -9,6 +9,7 @@
 #include "base/mac/bundle_locations.h"
 #include "base/mac/mac_util.h"
 #include "base/memory/singleton.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/string_util.h"
 #include "base/sys_string_conversions.h"
 #include "base/utf_string_conversions.h"
@@ -105,7 +106,9 @@ namespace ToolbarControllerInternal {
 // A class registered for C++ notifications. This is used to detect changes in
 // preferences and upgrade available notifications. Bridges the notification
 // back to the ToolbarController.
-class NotificationBridge : public content::NotificationObserver {
+class NotificationBridge
+    : public content::NotificationObserver,
+      public PrefObserver {
  public:
   explicit NotificationBridge(ToolbarController* controller)
       : controller_(controller) {
@@ -118,11 +121,8 @@ class NotificationBridge : public content::NotificationObserver {
   // Overridden from content::NotificationObserver:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
-                       const content::NotificationDetails& details) {
+                       const content::NotificationDetails& details) OVERRIDE {
     switch (type) {
-      case chrome::NOTIFICATION_PREF_CHANGED:
-        [controller_ prefChanged:content::Details<std::string>(details).ptr()];
-        break;
       case chrome::NOTIFICATION_UPGRADE_RECOMMENDED:
       case chrome::NOTIFICATION_GLOBAL_ERRORS_CHANGED:
         [controller_ badgeWrenchMenuIfNeeded];
@@ -132,6 +132,12 @@ class NotificationBridge : public content::NotificationObserver {
     }
   }
 
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE {
+    [controller_ prefChanged:&pref_name];
+  }
+
  private:
   ToolbarController* controller_;  // weak, owns us