content: convert zoom notifications to observer usage

chrome/browser/profiles/profile_impl.h

Index: chrome/browser/profiles/profile_impl.h
diff --git a/chrome/browser/profiles/profile_impl.h b/chrome/browser/profiles/profile_impl.h
index d25fae4dde552707ec686f07d993247f09b91a98..2de5a94371559a923f7ad58e6766061927d3563e 100644
--- a/chrome/browser/profiles/profile_impl.h
+++ b/chrome/browser/profiles/profile_impl.h
@@ -17,6 +17,7 @@
 #include "base/timer.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_impl_io_data.h"
+#include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
@@ -51,6 +52,7 @@ class UserCloudPolicyManager;
 
 // The default profile implementation.
 class ProfileImpl : public Profile,
+                    public content::HostZoomMap::Observer,
                     public content::NotificationObserver {
  public:
   // Value written to prefs when the exit type is EXIT_NORMAL. Public for tests.
@@ -130,6 +132,9 @@ class ProfileImpl : public Profile,
 
   virtual PrefProxyConfigTracker* GetProxyConfigTracker() OVERRIDE;
 
+  // content::HostZoomMap::Observer implementation:
+  virtual void OnZoomLevelChanged(const std::string& host) OVERRIDE;
+
   // content::NotificationObserver implementation.
   virtual void Observe(int type,
                        const content::NotificationSource& source,