Fix some flaky tests.

content/public/test/test_frame_navigation_observer.cc

Index: content/public/test/test_frame_navigation_observer.cc
diff --git a/content/public/test/test_frame_navigation_observer.cc b/content/public/test/test_frame_navigation_observer.cc
index e5a19430143f939ecdbe9c60fbccd033db06f137..e16c7d9a3764e1a14add6307abddbd881d81a97b 100644
--- a/content/public/test/test_frame_navigation_observer.cc
+++ b/content/public/test/test_frame_navigation_observer.cc
@@ -33,7 +33,8 @@ TestFrameNavigationObserver::TestFrameNavigationObserver(
       navigation_started_(false),
       has_committed_(false),
       wait_for_commit_(false),
-      message_loop_runner_(new MessageLoopRunner) {
+      message_loop_runner_(
+          new MessageLoopRunner(MessageLoopRunner::QuitMode::IMMEDIATE)) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 }