ios: Cleanup class/struct forward declarations

ios/chrome/browser/installation_notifier.h

 // Copyright 2013 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_CHROME_BROWSER_INSTALLATION_NOTIFIER_H_
 #define IOS_CHROME_BROWSER_INSTALLATION_NOTIFIER_H_
 
 #import <Foundation/Foundation.h>
 #include <stdint.h>
 
-class GURL;
-
 // Protocol used to mock the delayed dispatching for the unit tests.
 // Calls |block| after |delayInNSec|.
 @protocol DispatcherProtocol<NSObject>
 - (void)dispatchAfter:(int64_t)delayInNSec withBlock:(dispatch_block_t)block;
 @end
 
 @interface InstallationNotifier : NSObject
 // Returns singleton instance.
 + (InstallationNotifier*)sharedInstance;
 
 // Registers |observer| to be sent a notification named |scheme| when a URL
 // with |scheme| can be opened. |observer| must not be nil. If |scheme| is nil
 // or an empty string, |observer| is not registered for anything.
 - (void)registerForInstallationNotifications:(id)observer
                                 withSelector:(SEL)notificationSelector
                                    forScheme:(NSString*)scheme;
 
 // Unregisters all the NSNotifications ever asked by |observer|.
 - (void)unregisterForNotifications:(id)observer;
 
 // Performs a check for installed apps right away and restarts the polling.
 // There is usually no need for registered observers to call this method, unless
 // registered observers need to know the accurate state of installed native
 // apps.
 - (void)checkNow;
 @end
 
 #endif  // IOS_CHROME_BROWSER_INSTALLATION_NOTIFIER_H_