Add unit tests for the 'disable-sync' flag

chrome/browser/sync/profile_sync_service_factory_unittest.cc

+// Copyright (c) 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 "base/command_line.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/sync/profile_sync_service_factory.h"
+#include "chrome/common/chrome_switches.h"
+#include "chrome/test/base/testing_profile.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+class ProfileSyncServiceFactoryTest : public testing::Test {
+ protected:
+  ProfileSyncServiceFactoryTest() {}
+
+  void SetUp() override {
+    profile_.reset(new TestingProfile());
+  }
+
+  scoped_ptr<Profile> profile_;
+};
+
+// Verify that the disable sync flag disables creation of the sync service.
+TEST_F(ProfileSyncServiceFactoryTest, DisableSyncFlag) {
+  base::CommandLine::ForCurrentProcess()->AppendSwitch(switches::kDisableSync);
+  EXPECT_EQ(nullptr, ProfileSyncServiceFactory::GetForProfile(profile_.get()));
+}