Fixed typo in InterstitialDismissed method name.

ios/web/public/web_state/web_state_observer.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_OBSERVER_H_
 #define IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_OBSERVER_H_
 
 #include <stddef.h>
 
 #include <string>
@@ skipping 40 matching lines @@
   // Called when the current page has started loading.
   virtual void DidStartLoading() {}
 
   // Called when the current page has stopped loading.
   virtual void DidStopLoading() {}
 
   // Called when the current page is loaded.
   virtual void PageLoaded(PageLoadCompletionStatus load_completion_status) {}
 
   // Called when the interstitial is dismissed by the user.
-  virtual void InsterstitialDismissed() {}
+  virtual void InterstitialDismissed() {}
 
   // Called on URL hash change events.
   virtual void UrlHashChanged() {}
 
   // Called on history state change events.
   virtual void HistoryStateChanged() {}
 
   // Notifies the observer that the page has made some progress loading.
   // |progress| is a value between 0.0 (nothing loaded) to 1.0 (page fully
   // loaded).
@@ skipping 94 matching lines @@
   void ResetWebState();
 
   WebState* web_state_;
 
   DISALLOW_COPY_AND_ASSIGN(WebStateObserver);
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_WEB_STATE_WEB_STATE_OBSERVER_H_