[ios] Adds code to support the iOS Handoff feature.

components/handoff/handoff_manager.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 COMPONENTS_HANDOFF_HANDOFF_MANAGER_H_
 #define COMPONENTS_HANDOFF_HANDOFF_MANAGER_H_
 
 #include <Foundation/Foundation.h>
 
 #include "base/mac/objc_property_releaser.h"
+#include "build/build_config.h"
 #include "components/handoff/handoff_utility.h"
 #include "url/gurl.h"
 
 @class NSUserActivity;
 
+#if defined(OS_IOS)
+namespace user_prefs {
+class PrefRegistrySyncable;
+}  // namespace user_prefs
+#endif
+
 // Maintains all of the state relevant to the Handoff feature. Allows Chrome to
 // hand off the current active URL to other devices.
 @interface HandoffManager : NSObject {
  @private
   base::mac::ObjCPropertyReleaser _propertyReleaser_HandoffManager;
 
   GURL _activeURL;
   NSUserActivity* _userActivity;
   handoff::Origin _origin;
 }
 
+#if defined(OS_IOS)
+// Registers preferences related to Handoff.
++ (void)registerBrowserStatePrefs:(user_prefs::PrefRegistrySyncable*)registry;
+#endif
+
 // The active URL is defined as the URL of the most recently accessed tab. This
 // method should be called any time the active URL might have changed. This
 // method is idempotent.
 - (void)updateActiveURL:(const GURL&)url;
 
 @end
 
+@interface HandoffManager (TestingOnly)
+- (NSURL*)userActivityWebpageURL;
+@end
+
 #endif  // COMPONENTS_HANDOFF_HANDOFF_MANAGER_H_