Fix GcmApiTest with NavigationLoaderOnUI enabled

ProfileSyncService may not be created if a command line flag turns off
sync. In this case, ProfileSyncServiceFactory::GetForProfile returns
null and crashes when IsSyncFeatureEnabled is called.

Bug: 978617
Change-Id: Idb381a82008065427d67d87583f56eca9d1e9606
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1715094
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680137}

chrome/browser/signin/header_modification_delegate_on_ui_thread_impl.cc

@@ -57,6 +57,10 @@ void HeaderModificationDelegateOnUIThreadImpl::ProcessRequest(
     const GURL& redirect_url) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   const PrefService* prefs = profile_->GetPrefs();
+#if BUILDFLAG(ENABLE_DICE_SUPPORT)
+  syncer::SyncService* sync_service =
+      ProfileSyncServiceFactory::GetForProfile(profile_);
+#endif
   FixAccountConsistencyRequestHeader(
       request_adapter, redirect_url, profile_->IsOffTheRecord(),
       prefs->GetInteger(prefs::kIncognitoModeAvailability),
@@ -66,8 +70,7 @@ void HeaderModificationDelegateOnUIThreadImpl::ProcessRequest(
       prefs->GetBoolean(prefs::kAccountConsistencyMirrorRequired),
 #endif
 #if BUILDFLAG(ENABLE_DICE_SUPPORT)
-      ProfileSyncServiceFactory::GetForProfile(profile_)
-          ->IsSyncFeatureEnabled(),
+      sync_service && sync_service->IsSyncFeatureEnabled(),
       prefs->GetString(prefs::kGoogleServicesSigninScopedDeviceId),
 #endif
       cookie_settings_.get());

testing/buildbot/filters/navigation_loader_on_ui_browser_tests.filter

 # These tests currently fail when run with --enable-features=NavigationLoaderOnUI
-
-# https://crbug.com/978617
--GcmApiTest.*