Use RenderProcessHost::Shutdown in test to avoid flakiness.

content/browser/frame_host/frame_tree_browsertest.cc

Index: content/browser/frame_host/frame_tree_browsertest.cc
diff --git a/content/browser/frame_host/frame_tree_browsertest.cc b/content/browser/frame_host/frame_tree_browsertest.cc
index 9ce4131f87773a340eb7e7bcd837cd40803c5698..ac1b31f7710a413c2886b5fc6fc1c7385b3bbe97 100644
--- a/content/browser/frame_host/frame_tree_browsertest.cc
+++ b/content/browser/frame_host/frame_tree_browsertest.cc
@@ -135,7 +135,8 @@ IN_PROC_BROWSER_TEST_F(FrameTreeBrowserTest, FrameTreeAfterCrash) {
   RenderProcessHostWatcher crash_observer(
       shell()->web_contents(),
       RenderProcessHostWatcher::WATCH_FOR_PROCESS_EXIT);
-  NavigateToURL(shell(), GURL(kChromeUICrashURL));
+  ASSERT_TRUE(
+      shell()->web_contents()->GetMainFrame()->GetProcess()->Shutdown(0, true));
   crash_observer.Wait();
 
   // The frame tree should be cleared.