Chrome OS: hide experimeltal user service id "usm" behind a flag.

Not yet suported service "usm" needs to be behind flag CrOSEnableUSMUserService.

Bug: 837107
Change-Id: If3bfc4d58d1894074fb7b50c94b8fe91ee459e5a
Reviewed-on: https://chromium-review.googlesource.com/1038813Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Alexander Alekseev <alemate@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555488}

chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc

@@ -224,7 +224,12 @@ void GetVersionAndConsent(std::string* out_version, bool* out_consent) {
 user_manager::UserType GetUsertypeFromServicesString(
     const ::login::StringList& services) {
   bool is_child = false;
-  const base::flat_set<std::string> known_flags = {"uca", "usm"};
+  const bool support_usm =
+      base::FeatureList::IsEnabled(features::kCrOSEnableUSMUserService);
+  using KnownFlags = base::flat_set<std::string>;
+  const KnownFlags known_flags =
+      support_usm ? KnownFlags({"uca", "usm"}) : KnownFlags({"uca"});
+
   size_t i = 0;
   for (const std::string& item : services) {
     if (known_flags.find(item) != known_flags.end()) {

chrome/common/chrome_features.cc

@@ -650,6 +650,11 @@ const base::Feature kEasyUnlockPromotions{"EasyUnlockPromotions",
 const base::Feature kTPMFirmwareUpdate{"TPMFirmwareUpdate",
                                        base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables or disables "usm" service in the list of user services returned by
+// userInfo Gaia message.
+const base::Feature kCrOSEnableUSMUserService{
+    "CrOSEnableUSMUserService", base::FEATURE_DISABLED_BY_DEFAULT};
+
 #endif  // defined(OS_CHROMEOS)
 
 }  // namespace features

chrome/common/chrome_features.h

@@ -351,6 +351,8 @@ extern const base::Feature kInstantTethering;
 extern const base::Feature kEasyUnlockPromotions;
 
 extern const base::Feature kTPMFirmwareUpdate;
+
+extern const base::Feature kCrOSEnableUSMUserService;
 #endif  // defined(OS_CHROMEOS)
 
 bool PrefServiceEnabled();