Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h

Index: chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h
diff --git a/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h b/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h
index 3290143ded04497fda12f3616ea93223a6365492..bba88ff95a2eb6e3f8e53dee141b3e20fdbdfd5e 100644
--- a/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h
+++ b/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h
@@ -13,6 +13,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/extensions/image_loading_tracker.h"
 #include "chrome/browser/ui/browser.h"
@@ -45,7 +46,8 @@ class ZoomDecoration;
 class LocationBarViewMac : public LocationBar,
                            public LocationBarTesting,
                            public OmniboxEditController,
-                           public content::NotificationObserver {
+                           public content::NotificationObserver,
+                           public PrefObserver {
  public:
   LocationBarViewMac(AutocompleteTextField* field,
                      CommandUpdater* command_updater,
@@ -181,6 +183,10 @@ class LocationBarViewMac : public LocationBar,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   Browser* browser() const { return browser_; }
 
  private: