[cros] Add --stub-cros-settings option for testing.

chrome/browser/chromeos/cros_settings_provider.cc

Index: chrome/browser/chromeos/cros_settings_provider.cc
diff --git a/chrome/browser/chromeos/cros_settings_provider.cc b/chrome/browser/chromeos/cros_settings_provider.cc
index 1eeaf5d414c2c8cf954895648eaa4f7232d8c50f..07cf7cd47ddcf26b9f40895ef924d91a3c474541 100644
--- a/chrome/browser/chromeos/cros_settings_provider.cc
+++ b/chrome/browser/chromeos/cros_settings_provider.cc
@@ -12,6 +12,11 @@
 
 namespace chromeos {
 
+CrosSettingsProvider::CrosSettingsProvider(
+    const NotifyObserversCallback& notify_cb)
+  : notify_cb_(notify_cb) {
+}
+
 void CrosSettingsProvider::Set(const std::string& path,
                                const base::Value& value) {
   // We don't allow changing any of the cros settings without prefix
@@ -25,4 +30,8 @@ void CrosSettingsProvider::Set(const std::string& path,
   DoSet(path, value);
 }
 
+void CrosSettingsProvider::NotifyObservers(const std::string& path) {
+  notify_cb_.Run(path);
+}
+
 };  // namespace chromeos