extensions: Cleanup class/struct fwd declarations

extensions/browser/api/extensions_api_client.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 EXTENSIONS_BROWSER_API_EXTENSIONS_API_CLIENT_H_
 #define EXTENSIONS_BROWSER_API_EXTENSIONS_API_CLIENT_H_
 
 #include <map>
 #include <memory>
 
 #include "base/memory/ref_counted.h"
 #include "extensions/browser/api/declarative_content/content_rules_registry.h"
 #include "extensions/browser/api/storage/settings_namespace.h"
 
-class GURL;
-
 namespace base {
 template <class T>
 class ObserverListThreadSafe;
 }
 
 namespace content {
 class BrowserContext;
 class WebContents;
 }
 
@@ skipping 105 matching lines @@
   // MetricsPrivateAPI behavior.
   virtual MetricsPrivateDelegate* GetMetricsPrivateDelegate();
 
   // NOTE: If this interface gains too many methods (perhaps more than 20) it
   // should be split into one interface per API.
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_API_EXTENSIONS_API_CLIENT_H_