[zoom bubble] Add tests for ZoomController::UpdateState() handling empty hosts.

chrome/browser/ui/zoom/zoom_controller.h

Index: chrome/browser/ui/zoom/zoom_controller.h
diff --git a/chrome/browser/ui/zoom/zoom_controller.h b/chrome/browser/ui/zoom/zoom_controller.h
index 4e8beafa122a12ae03e6b81660d2af9f55761ce6..ad0562472030b8f8111843c2ea556c0040a93f00 100644
--- a/chrome/browser/ui/zoom/zoom_controller.h
+++ b/chrome/browser/ui/zoom/zoom_controller.h
@@ -36,11 +36,6 @@ class ZoomController : public content::NotificationObserver,
 
   void set_observer(ZoomObserver* observer) { observer_ = observer; }
 
- private:
-  friend class content::WebContentsUserData<ZoomController>;
-
-  explicit ZoomController(content::WebContents* web_contents);
-
   // content::WebContentsObserver overrides:
   virtual void DidNavigateMainFrame(
       const content::LoadCommittedDetails& details,
@@ -51,6 +46,11 @@ class ZoomController : public content::NotificationObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+ private:
+  explicit ZoomController(content::WebContents* web_contents);
+  friend class content::WebContentsUserData<ZoomController>;
+  friend class ZoomControllerTest;
+
   // Updates the zoom icon and zoom percentage based on current values and
   // notifies the observer if changes have occurred. |host| may be empty,
   // meaning the change should apply to ~all sites. If it is not empty, the