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

ios/chrome/browser/device_sharing/BUILD.gn

 # Copyright 2016 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.
 
-source_set("itunes_links") {
+source_set("device_sharing") {
   sources = [
-    "itunes_links_observer.h",
-    "itunes_links_observer.mm",
+    "device_sharing_manager.h",
+    "device_sharing_manager.mm",
   ]
   deps = [
     "//base",
+    "//components/handoff",
+    "//components/prefs",
     "//ios/chrome/browser",
-    "//ios/web",
+    "//ios/chrome/browser/browser_state",
+    "//ios/chrome/browser/prefs",
+    "//net",
     "//url",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
-    "itunes_links_observer_unittest.mm",
+    "device_sharing_manager_unittest.mm",
   ]
   deps = [
-    ":itunes_links",
+    ":device_sharing",
     "//base",
+    "//components/handoff",
+    "//components/sync_preferences:test_support",
     "//ios/chrome/browser",
+    "//ios/chrome/browser/browser_state:test_support",
     "//ios/web:test_support",
     "//testing/gtest",
     "//third_party/ocmock",
     "//url",
   ]
 }