Wait for OobeWebUI to finish loading before running tests.

chrome/browser/chromeos/login/test/oobe_base_test.cc

Index: chrome/browser/chromeos/login/test/oobe_base_test.cc
diff --git a/chrome/browser/chromeos/login/test/oobe_base_test.cc b/chrome/browser/chromeos/login/test/oobe_base_test.cc
index 5d5a5278d5e29daf932a66ab9713c5751b4346d0..52d6f6cc47999f7d2911e3dfed2e14abc0ad2add 100644
--- a/chrome/browser/chromeos/login/test/oobe_base_test.cc
+++ b/chrome/browser/chromeos/login/test/oobe_base_test.cc
@@ -7,6 +7,7 @@
 #include "base/command_line.h"
 #include "base/message_loop/message_loop.h"
 #include "base/path_service.h"
+#include "base/run_loop.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/chromeos/login/existing_user_controller.h"
 #include "chrome/browser/chromeos/login/session/user_session_manager.h"
@@ -111,6 +112,13 @@ void OobeBaseTest::SetUpOnMainThread() {
 
   LoginDisplayHostImpl::DisableRestrictiveProxyCheckForTest();
 
+  // Wait for OobeUI to finish loading.
+  base::RunLoop run_loop;
+  if (!LoginDisplayHost::default_host()->GetOobeUI()->IsJSReady(
+          run_loop.QuitClosure())) {
+    run_loop.Run();
+  }
+
   ExtensionApiTest::SetUpOnMainThread();
 }