Split //ios/chrome/browser/prefs to prevent circular dependencies.

ios/chrome/browser/device_sharing/device_sharing_manager_unittest.mm

 // Copyright 2015 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 "ios/chrome/browser/device_sharing/device_sharing_manager.h"
 
 #include <memory>
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_nsobject.h"
 #import "components/handoff/handoff_manager.h"
+#include "components/handoff/pref_names_ios.h"
 #include "components/sync_preferences/testing_pref_service_syncable.h"
 #include "ios/chrome/browser/browser_state/test_chrome_browser_state.h"
-#include "ios/chrome/browser/pref_names.h"
 #include "ios/web/public/test/test_web_thread_bundle.h"
 #include "testing/platform_test.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
 #import "third_party/ocmock/gtest_support.h"
 #include "url/gurl.h"
 
 @interface TestDeviceSharingManager : DeviceSharingManager
 + (HandoffManager*)createHandoffManager;
 @end
 
@@ skipping 82 matching lines @@
 TEST_F(DeviceSharingManagerTest, DisableHandoffViaPrefs) {
   [sharing_manager_ updateBrowserState:chrome_browser_state_.get()];
   EXPECT_TRUE([sharing_manager_ handoffManager]);
   sync_preferences::TestingPrefServiceSyncable* prefs =
       chrome_browser_state_->GetTestingPrefService();
   prefs->SetBoolean(prefs::kIosHandoffToOtherDevices, false);
   EXPECT_FALSE([sharing_manager_ handoffManager]);
 }
 
 }  // namespace