Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/views/toolbar_view.h

Index: chrome/browser/ui/views/toolbar_view.h
diff --git a/chrome/browser/ui/views/toolbar_view.h b/chrome/browser/ui/views/toolbar_view.h
index b126f89f8860909db0bfe1c6fad4f1c1e627b5ca..4e6e244507d39ee9bccc9add71f306f5e744328c 100644
--- a/chrome/browser/ui/views/toolbar_view.h
+++ b/chrome/browser/ui/views/toolbar_view.h
@@ -10,6 +10,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/command_observer.h"
 #include "chrome/browser/ui/toolbar/back_forward_menu_model.h"
@@ -39,7 +40,8 @@ class ToolbarView : public views::AccessiblePaneView,
                     public content::NotificationObserver,
                     public CommandObserver,
                     public views::ButtonListener,
-                    public views::WidgetObserver {
+                    public views::WidgetObserver,
+                    public PrefObserver {
  public:
   // The view class name.
   static const char kViewClassName[];
@@ -125,6 +127,10 @@ class ToolbarView : public views::AccessiblePaneView,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // Overridden from PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Overridden from ui::AcceleratorProvider:
   virtual bool GetAcceleratorForCommandId(
       int command_id, ui::Accelerator* accelerator) OVERRIDE;