[USS] Covert kSyncEnableUSSDeviceInfo commandline flag to Feature API

BUG=647492

Review-Url: https://codereview.chromium.org/2341923004
Cr-Commit-Position: refs/heads/master@{#419176}

components/browser_sync/browser/profile_sync_components_factory_impl.cc

@@ -150,8 +150,7 @@ void ProfileSyncComponentsFactoryImpl::RegisterCommonDataTypes(
       base::Bind(&ChromeReportUnrecoverableError, channel_);
 
   // TODO(stanisc): can DEVICE_INFO be one of disabled datatypes?
-  if (channel_ == version_info::Channel::UNKNOWN &&
-      command_line_.HasSwitch(switches::kSyncEnableUSSDeviceInfo)) {
+  if (base::FeatureList::IsEnabled(switches::kSyncUSSDeviceInfo)) {
     sync_service->RegisterDataTypeController(
         base::MakeUnique<UIModelTypeController>(syncer::DEVICE_INFO,
                                                 error_callback, sync_client_));

components/browser_sync/browser/profile_sync_service.cc

@@ -294,9 +294,7 @@ void ProfileSyncService::Initialize() {
                  sync_enabled_weak_factory_.GetWeakPtr(),
                  syncer::ModelTypeSet(syncer::SESSIONS))));
 
-  if (channel_ == version_info::Channel::UNKNOWN &&
-      base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kSyncEnableUSSDeviceInfo)) {
+  if (base::FeatureList::IsEnabled(switches::kSyncUSSDeviceInfo)) {
     scoped_refptr<base::SequencedTaskRunner> blocking_task_runner(
         blocking_pool_->GetSequencedTaskRunnerWithShutdownBehavior(
             blocking_pool_->GetSequenceToken(),

components/sync/driver/sync_driver_switches.cc

@@ -17,11 +17,6 @@ const char kSyncDisableDeferredStartup[] = "sync-disable-deferred-startup";
 // Enables feature to avoid unnecessary GetUpdate requests.
 const char kSyncEnableGetUpdateAvoidance[] = "sync-enable-get-update-avoidance";
 
-// Enables USS implementation of DeviceInfo datatype. This flag controls whether
-// SyncableService based or ModelTypeService based implementation is used for
-// DeviceInfo type.
-const char kSyncEnableUSSDeviceInfo[] = "sync-enable-uss-device-info";
-
 // Overrides the default server used for profile sync.
 const char kSyncServiceURL[] = "sync-url";
 
@@ -34,4 +29,10 @@ const char kSyncShortInitialRetryOverride[] =
 const base::Feature kSyncClearDataOnPassphraseEncryption{
     "ClearSyncDataOnPassphraseEncryption", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables USS implementation of DeviceInfo datatype. This flag controls whether
+// SyncableService based or ModelTypeService based implementation is used for
+// DeviceInfo type.
+const base::Feature kSyncUSSDeviceInfo{"EnableSyncUSSDeviceInfo",
+                                       base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace switches

components/sync/driver/sync_driver_switches.h

@@ -16,11 +16,11 @@ namespace switches {
 extern const char kSyncDeferredStartupTimeoutSeconds[];
 extern const char kSyncDisableDeferredStartup[];
 extern const char kSyncEnableGetUpdateAvoidance[];
-extern const char kSyncEnableUSSDeviceInfo[];
 extern const char kSyncServiceURL[];
 extern const char kSyncShortInitialRetryOverride[];
 
 extern const base::Feature kSyncClearDataOnPassphraseEncryption;
+extern const base::Feature kSyncUSSDeviceInfo;
 
 }  // namespace switches