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

components/handoff/handoff_manager.mm

 // 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.
 
 #include "components/handoff/handoff_manager.h"
 
 #include "base/logging.h"
 #include "base/mac/scoped_nsobject.h"
-#include "build/build_config.h"
 #include "net/base/mac/url_conversions.h"
 
 #if defined(OS_IOS)
 #include "base/ios/ios_util.h"
+#include "components/handoff/pref_names_ios.h"
+#include "components/pref_registry/pref_registry_syncable.h"  // nogncheck

[erikchen, 2016/11/08 18:13:55]

why do you need nogncheck?

[rohitrao (ping after 24h), 2016/11/08 19:57:35]

I added the components/pref_registry dependency only to the iOS build, so this
include would fail the GN header check on mac.

I could alternatively add the dependency on all platforms, even though it's not
needed on mac.

 #endif
 
 #if defined(OS_MACOSX) && !defined(OS_IOS)
 #include "base/mac/mac_util.h"
 #include "base/mac/sdk_forward_declarations.h"
 #endif
 
 @interface HandoffManager ()
 
 // The active user activity.
 @property(nonatomic, retain) NSUserActivity* userActivity;
 
 // Whether the URL of the current tab should be exposed for Handoff.
 - (BOOL)shouldUseActiveURL;
 
 // Updates the active NSUserActivity.
 - (void)updateUserActivity;
 
 @end
 
 @implementation HandoffManager
 
 @synthesize userActivity = _userActivity;
 
+#if defined(OS_IOS)
++ (void)registerBrowserStatePrefs:(user_prefs::PrefRegistrySyncable*)registry {
+  registry->RegisterBooleanPref(
+      prefs::kIosHandoffToOtherDevices, true,
+      user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
+}
+#endif
+
 - (instancetype)init {
   self = [super init];
   if (self) {
     _propertyReleaser_HandoffManager.Init(self, [HandoffManager class]);
 #if defined(OS_MACOSX) && !defined(OS_IOS)
     _origin = handoff::ORIGIN_MAC;
 #elif defined(OS_IOS)
     _origin = handoff::ORIGIN_IOS;
 #else
     NOTREACHED();
@@ skipping 43 matching lines @@
            withObject:handoff::kChromeHandoffActivityType];
   self.userActivity = base::scoped_nsobject<NSUserActivity>(userActivity);
   self.userActivity.webpageURL = net::NSURLWithGURL(_activeURL);
   NSString* origin = handoff::StringFromOrigin(_origin);
   DCHECK(origin);
   self.userActivity.userInfo = @{ handoff::kOriginKey : origin };
   [self.userActivity becomeCurrent];
 }
 
 @end
+
+@implementation HandoffManager (TestingOnly)
+
+- (NSURL*)userActivityWebpageURL {
+  return self.userActivity.webpageURL;
+}
+
+@end