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

components/handoff/handoff_manager.h

Index: components/handoff/handoff_manager.h
diff --git a/components/handoff/handoff_manager.h b/components/handoff/handoff_manager.h
index b29394d717391d473795d868e55b6d635437c01b..19bde22ee543f6b74d248f4ffae3e1f6e3cea3f9 100644
--- a/components/handoff/handoff_manager.h
+++ b/components/handoff/handoff_manager.h
@@ -8,11 +8,18 @@
 #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 {
@@ -24,6 +31,11 @@
   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.
@@ -31,4 +43,8 @@
 
 @end
 
+@interface HandoffManager (TestingOnly)
+- (NSURL*)userActivityWebpageURL;
+@end
+
 #endif  // COMPONENTS_HANDOFF_HANDOFF_MANAGER_H_