Revert 170483 - Remove PrefObserver usages, batch 12.

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

Index: chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
===================================================================
--- chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm	(revision 170518)
+++ chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm	(working copy)
@@ -139,11 +139,8 @@
       chrome::NOTIFICATION_EXTENSION_LOCATION_BAR_UPDATED,
       content::Source<Profile>(browser_->profile()));
 
-  edit_bookmarks_enabled_.Init(
-      prefs::kEditBookmarksEnabled,
-      profile_->GetPrefs(),
-      base::Bind(&LocationBarViewMac::OnEditBookmarksEnabledChanged,
-                 base::Unretained(this)));
+  edit_bookmarks_enabled_.Init(prefs::kEditBookmarksEnabled,
+                               profile_->GetPrefs(), this);
 }
 
 LocationBarViewMac::~LocationBarViewMac() {
@@ -600,7 +597,8 @@
   }
 }
 
-void LocationBarViewMac::OnEditBookmarksEnabledChanged() {
+void LocationBarViewMac::OnPreferenceChanged(PrefServiceBase* service,
+                                             const std::string& pref_name) {
   UpdateStarDecorationVisibility();
   OnChanged();
 }