Don't unconditionally access verifier() in TwoClientSearchEnginesSyncTest

The verifier profile doesn't always exist; notably it doesn't when
running against external servers (aka E2E_TEST, aka KitchenSync).
This fixes a test crash when running in that mode.

Bug: 1135195
Change-Id: I163583c74e2139cd50f9d658657832d57550a3ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2450290
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Auto-Submit: Marc Treib <treib@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814125}

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

@@ -29,8 +29,12 @@ class TwoClientSearchEnginesSyncTest : public SyncTest {
     }
 
     // Wait for models to load.
-    search_test_utils::WaitForTemplateURLServiceToLoad(
-        TemplateURLServiceFactory::GetForProfile(verifier()));
+    if (use_verifier()) {
+      // Note: The verifier profile isn't used when running against external
+      // servers.
+      search_test_utils::WaitForTemplateURLServiceToLoad(
+          TemplateURLServiceFactory::GetForProfile(verifier()));
+    }
     search_test_utils::WaitForTemplateURLServiceToLoad(
         TemplateURLServiceFactory::GetForProfile(GetProfile(0)));
     search_test_utils::WaitForTemplateURLServiceToLoad(