Fix ChromeLauncherController tests when SplitSettingsSync is enabled

Some of the tests assume that OS sync is enabled, which is not the
default. Explicitly enable OS sync in test setup.

This is preparation for making SplitSettingsSync on-by-default.

Bug: 1013466
Change-Id: Icf0f2ff92083702d6f7a1fcc9fde0ce54569d9ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2210626Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770667}

chrome/browser/ui/ash/launcher/chrome_launcher_controller_unittest.cc

@@ -354,6 +354,13 @@ class ChromeLauncherControllerTest
     extension_system->ready().Post(FROM_HERE, run_loop.QuitClosure());
     run_loop.Run();
 
+    // Many pinned app tests assume OS sync is enabled.
+    if (chromeos::features::IsSplitSettingsSyncEnabled()) {
+      syncer::SyncService* sync_service =
+          ProfileSyncServiceFactory::GetForProfile(profile());
+      sync_service->GetUserSettings()->SetOsSyncFeatureEnabled(true);
+    }
+
     app_list_syncable_service_ =
         app_list::AppListSyncableServiceFactory::GetForProfile(profile());
     StartAppSyncService(app_list_syncable_service_->GetAllSyncDataForTesting());