Spelling correction: "nonexistant" -> "nonexistent".

chrome/browser/cancelable_request.h

 // Copyright (c) 2010 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.
 
 // CancelableRequestProviders and Consumers work together to make requests that
 // execute on a background thread in the provider and return data to the
 // consumer. These class collaborate to keep a list of open requests and to
 // make sure that requests to not outlive either of the objects involved in the
 // transaction.
 //
@@ skipping 279 matching lines @@
     DCHECK(pending_requests_.find(PendingRequest(provider, handle)) ==
            pending_requests_.end());
     pending_requests_[PendingRequest(provider, handle)] = get_initial_t();
   }
 
   virtual void OnRequestRemoved(CancelableRequestProvider* provider,
                                 CancelableRequestProvider::Handle handle) {
     typename PendingRequestList::iterator i =
         pending_requests_.find(PendingRequest(provider, handle));
     if (i == pending_requests_.end()) {
-      NOTREACHED() << "Got a complete notification for a nonexistant request";
+      NOTREACHED() << "Got a complete notification for a nonexistent request";
       return;
     }
 
     pending_requests_.erase(i);
   }
 
   // Lists all outstanding requests.
   PendingRequestList pending_requests_;
 };
 
@@ skipping 248 matching lines @@
   }
 
   // The value.
   Type value;
 
  protected:
   virtual ~CancelableRequest1() {}
 };
 
 #endif  // CHROME_BROWSER_CANCELABLE_REQUEST_H__