Use RenderProcessHost::Shutdown in test to avoid flakiness.

content/browser/frame_host/frame_tree_browsertest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "content/browser/frame_host/frame_tree.h"
 #include "content/browser/frame_host/frame_tree_node.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
@@ skipping 117 matching lines @@
   RenderViewHost* rvh = shell()->web_contents()->GetRenderViewHost();
   RenderFrameHostImpl* rfh =
       static_cast<RenderFrameHostImpl*>(rvh->GetMainFrame());
   EXPECT_TRUE(rvh->IsRenderViewLive());
   EXPECT_TRUE(rfh->IsRenderFrameLive());
 
   // Crash the renderer so that it doesn't send any FrameDetached messages.
   RenderProcessHostWatcher crash_observer(
       shell()->web_contents(),
       RenderProcessHostWatcher::WATCH_FOR_PROCESS_EXIT);
-  NavigateToURL(shell(), GURL(kChromeUICrashURL));
+  shell()->web_contents()->GetMainFrame()->GetProcess()->Shutdown(0, false);

[Łukasz Anforowicz, 2017/06/01 16:10:29]

It's probably a good idea to check (probably via EXPECT_TRUE rather than
ASSERT_TRUE) the return value from Shutdown (it can be failure-indicating-false
if !child_process_launcher_.get() or IsStarting().

I wonder if we should pass |true| as the second argument - I see in
base::Process::Terminate that it starts with SIGTERM, but when |wait| is true
and the process takes a long time to die, then it also does SIGKILL.  OTOH, if
the process hung, then I guess chrome://crash would also take a long time...
(but then maybe this is the source of flakiness that we are trying to avoid...).

[Charlie Reis, 2017/06/01 17:04:16]

Good idea.  But this is one of the cases that ASSERT_TRUE is good for-- the rest
of the test doesn't make sense if this kill fails, so it's good to early exit. 
The rest of the results won't have meaning otherwise.
Might as well-- we want this kill to be as effective as possible to make the
test meaningful.

   crash_observer.Wait();
 
   // The frame tree should be cleared.
   WebContentsImpl* wc = static_cast<WebContentsImpl*>(shell()->web_contents());
   FrameTreeNode* root = wc->GetFrameTree()->root();
   EXPECT_EQ(0UL, root->child_count());
 
   // Ensure the view and frame aren't live anymore.
   EXPECT_FALSE(rvh->IsRenderViewLive());
   EXPECT_FALSE(rfh->IsRenderFrameLive());
@@ skipping 605 matching lines @@
   // Make sure we did a process transfer back to "b.is".
   EXPECT_EQ(
       " Site A ------------ proxies for B\n"
       "   +--Site B ------- proxies for A\n"
       "Where A = http://a.com/\n"
       "      B = http://b.is/",
       FrameTreeVisualizer().DepictFrameTree(root));
 }
 
 }  // namespace content