Expose API on VariationsService to set the restrict mode param.

chrome/browser/chromeos/policy/variations_service_policy_browsertest.cc

Index: chrome/browser/chromeos/policy/variations_service_policy_browsertest.cc
diff --git a/chrome/browser/chromeos/policy/variations_service_policy_browsertest.cc b/chrome/browser/chromeos/policy/variations_service_policy_browsertest.cc
index 20f876c69895f2519eeadb3d151f0c226408f1ff..80503936aa982ac8dafb669f63bcaa5661706947 100644
--- a/chrome/browser/chromeos/policy/variations_service_policy_browsertest.cc
+++ b/chrome/browser/chromeos/policy/variations_service_policy_browsertest.cc
@@ -42,9 +42,8 @@ IN_PROC_BROWSER_TEST_F(VariationsServiceDevicePolicyTest, VariationsURLValid) {
           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));