Add DeviceSettingProvider unit tests.

chrome/test/base/testing_browser_process.cc

Index: chrome/test/base/testing_browser_process.cc
diff --git a/chrome/test/base/testing_browser_process.cc b/chrome/test/base/testing_browser_process.cc
index 64bee2c4b3d7ab6127d437a6c050f02daab56f2b..94af01a41b412f534dec32db5e802bd966692372 100644
--- a/chrome/test/base/testing_browser_process.cc
+++ b/chrome/test/base/testing_browser_process.cc
@@ -6,6 +6,7 @@
 
 #include "base/string_util.h"
 #include "chrome/browser/google/google_url_tracker.h"
+#include "chrome/browser/metrics/metrics_service.h"
 #include "chrome/browser/notifications/notification_ui_manager.h"
 #include "chrome/browser/policy/browser_policy_connector.h"
 #include "chrome/browser/policy/policy_service_stub.h"
@@ -39,7 +40,7 @@ void TestingBrowserProcess::EndSession() {
 }
 
 MetricsService* TestingBrowserProcess::metrics_service() {
-  return NULL;
+  return metrics_service_.get();
 }
 
 IOThread* TestingBrowserProcess::io_thread() {
@@ -270,3 +271,7 @@ void TestingBrowserProcess::SetSafeBrowsingService(
     SafeBrowsingService* sb_service) {
   sb_service_ = sb_service;
 }
+
+void TestingBrowserProcess::SetMetricsService(MetricsService* service) {
+  metrics_service_.reset(service);
+}