Take out pref watching from HostZoomMap, in preparation of removing Profile from it.

content/browser/host_zoom_map.h

Index: content/browser/host_zoom_map.h
===================================================================
--- content/browser/host_zoom_map.h	(revision 86148)
+++ content/browser/host_zoom_map.h	(working copy)
@@ -16,13 +16,11 @@
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
-#include "chrome/browser/prefs/pref_change_registrar.h"
 #include "content/browser/browser_thread.h"
 #include "content/common/notification_observer.h"
 #include "content/common/notification_registrar.h"
 
 class GURL;
-class PrefService;
 class Profile;
 
 // HostZoomMap needs to be deleted on the UI thread because it listens
@@ -34,8 +32,6 @@
  public:
   explicit HostZoomMap(Profile* profile);
 
-  static void RegisterUserPrefs(PrefService* prefs);
-
   // Returns the zoom level for a given url. The zoom level is determined by
   // the host portion of the URL, or (in the absence of a host) the complete
   // spec of the URL. In most cases, there is no custom zoom level, and this
@@ -73,6 +69,8 @@
                        const NotificationSource& source,
                        const NotificationDetails& details);
 
+  void set_default_zoom_level(double level) { default_zoom_level_ = level; }
+
  private:
   friend struct BrowserThread::DeleteOnThread<BrowserThread::UI>;
   friend class DeleteTask<HostZoomMap>;
@@ -81,13 +79,6 @@
 
   ~HostZoomMap();
 
-  // Reads the zoom levels from the preferences service.
-  void Load();
-
-  // Removes dependencies on the profile so we can live longer than
-  // the profile without crashing.
-  void Shutdown();
-
   // The profile we're associated with.
   Profile* profile_;
 
@@ -109,12 +100,7 @@
   // |temporary_zoom_levels_| to guarantee thread safety.
   mutable base::Lock lock_;
 
-  // Whether we are currently updating preferences, this is used to ignore
-  // notifications from the preference service that we triggered ourself.
-  bool updating_preferences_;
-
   NotificationRegistrar registrar_;
-  PrefChangeRegistrar pref_change_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(HostZoomMap);
 };