Expose API on VariationsService to set the restrict mode param.

chrome/browser/chromeos/policy/variations_service_policy_browsertest.cc

 // Copyright (c) 2013 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/strings/string_util.h"
 #include "chrome/browser/chromeos/policy/device_policy_builder.h"
 #include "chrome/browser/chromeos/policy/device_policy_cros_browser_test.h"
 #include "chrome/browser/chromeos/policy/proto/chrome_device_policy.pb.h"
 #include "chrome/browser/metrics/variations/variations_service.h"
 #include "chrome/test/base/testing_browser_process.h"
@@ skipping 24 matching lines @@
  private:
   DISALLOW_COPY_AND_ASSIGN(VariationsServiceDevicePolicyTest);
 };
 
 IN_PROC_BROWSER_TEST_F(VariationsServiceDevicePolicyTest, VariationsURLValid) {
   const std::string default_variations_url =
       chrome_variations::VariationsService::
           GetDefaultVariationsServerURLForTesting();
 
   // Device policy has updated the cros settings.
-  const GURL url =
-      chrome_variations::VariationsService::GetVariationsServerURL(
-          g_browser_process->local_state());
+  const GURL url = chrome_variations::VariationsService::GetVariationsServerURL(
+      g_browser_process->local_state(), std::string());
   EXPECT_TRUE(StartsWithASCII(url.spec(), default_variations_url, true));
   std::string value;
   EXPECT_TRUE(net::GetValueForKeyInQuery(url, "restrict", &value));
   EXPECT_EQ("restricted", value);
 }
 
 }  // namespace policy