Use real invalidation service for external tests

Bug: 1010568
Change-Id: I7f360ee361e486451aca2b21138c3a493a7d36a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1846474
Commit-Queue: Sven Zheng <svenzheng@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703905}

chrome/browser/sync/test/integration/sync_test.cc

@@ -930,6 +930,12 @@ void SyncTest::SetUpInProcessBrowserTestFixture() {
 
 void SyncTest::OnWillCreateBrowserContextServices(
     content::BrowserContext* context) {
+  if (UsingExternalServers()) {
+    // DO NOTHING. External live sync servers use GCM to notify profiles of
+    // any invalidations in sync'ed data. No need to provide a testing
+    // factory the ProfileInvalidationProvider.
+    return;
+  }
   invalidation::ProfileInvalidationProviderFactory::GetInstance()
       ->SetTestingFactory(
           context,