Fix some flaky tests.

content/browser/site_per_process_browsertest.cc

 // Copyright (c) 2012 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 "content/browser/site_per_process_browsertest.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 8339 matching lines @@
   EXPECT_EQ(1, child_count);
 
   // Add an unload handler to B's subframe.
   EXPECT_TRUE(
       ExecuteScript(root->child_at(0)->child_at(0)->current_frame_host(),
                     "window.onunload=function(e){\n"
                     "    window.location = '#navigate';\n"
                     "};\n"));
 
   // Navigate B's subframe to a cross-site C.
+  RenderFrameDeletedObserver deleted_observer(
+      root->child_at(0)->child_at(0)->current_frame_host());

[nasko, 2016/11/23 17:48:29]

I agree that moving this code makes sense. However, I don't follow your CL
comment about deleted_observer binding to the "c.com" RenderFrameHost. Even if
the navigation commits for c.com, there is no way for the observer to bind to
that RFH, as it will be root->child_at(0) and not
root->child_at(0)->child_at(0). What is possible is for the
root->child_at(0)->child_at(0) to be null of that happens.

[Alexander Semashko, 2016/11/23 18:38:08]

c.com is loaded in the third-level frame, because we navigate the child of
root->child_at(0).

[nasko, 2016/11/24 00:00:43]

Ah, yes!

   std::string script =
       std::string("window.document.getElementById('child-0').src = \"") +
       embedded_test_server()
           ->GetURL("c.com", "/cross_site_iframe_factory.html")
           .spec() +
       "\"";
   EXPECT_TRUE(
       ExecuteScript(root->child_at(0)->current_frame_host(), script.c_str()));
 
   // Wait until B's subframe RenderFrameHost is destroyed.
-  RenderFrameDeletedObserver deleted_observer(
-      root->child_at(0)->child_at(0)->current_frame_host());
   deleted_observer.WaitUntilDeleted();
 
   // Check that C's subframe is alive and the navigation in the unload handler
   // was ignored.
   EXPECT_TRUE(ExecuteScriptAndExtractInt(
       root->child_at(0)->child_at(0)->current_frame_host(),
       "window.domAutomationController.send(frames.length);", &child_count));
   EXPECT_EQ(0, child_count);
 
   EXPECT_EQ(
@@ skipping 270 matching lines @@
   // hit the 20 seconds delay before https://crbug.com/657195 was fixed.
   EXPECT_TRUE(NavigateToURL(shell(), page_url));
   EXPECT_EQ(page_url, shell()->web_contents()->GetLastCommittedURL());
 
   // Note: even if the test fails and for some reason, the test has not timed
   // out by this point, the test teardown code will still hit a DCHECK when it
   // calls AssertNoURLRequests() in the shell's URLRequestContext destructor.
 }
 
 }  // namespace content