Fix flakiness in postMessage-related SitePerProcessBrowserTests.

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 <algorithm>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 31 matching lines @@
 
 namespace {
 
 // Helper function to send a postMessage and wait for a reply message.  The
 // |post_message_script| is executed on the |sender_ftn| frame, and the sender
 // frame is expected to post |reply_status| from the DOMAutomationController
 // when it receives a reply.
 void PostMessageAndWaitForReply(FrameTreeNode* sender_ftn,
                                 const std::string& post_message_script,
                                 const std::string& reply_status) {
+  // Subtle: msg_queue needs to be declared before the ExecuteScript below, or
+  // else it might miss the message of interest.  See https://crbug.com/518729.
+  DOMMessageQueue msg_queue;
+
   bool success = false;
   EXPECT_TRUE(ExecuteScriptAndExtractBool(
       sender_ftn->current_frame_host(),
       "window.domAutomationController.send(" + post_message_script + ");",
       &success));
   EXPECT_TRUE(success);
 
-  content::DOMMessageQueue msg_queue;
   std::string status;
   while (msg_queue.WaitForMessage(&status)) {
     if (status == reply_status)
       break;
   }
 }
 
 // Helper function to extract and return "window.receivedMessages" from the
 // |sender_ftn| frame.  This variable is used in post_message.html to count the
 // number of messages received via postMessage by the current window.
@@ skipping 2402 matching lines @@
   // frame should have one message (reply from second frame).  Second frame
   // should have two messages (message from first frame and reply from parent).
   // Parent should have one message (from second frame).
   EXPECT_EQ(1, GetReceivedMessages(root->child_at(0)));
   EXPECT_EQ(2, GetReceivedMessages(root->child_at(1)));
   EXPECT_EQ(1, GetReceivedMessages(root));
 }
 
 // Check that postMessage can be sent from a subframe on a cross-process opener
 // tab, and that its event.source points to a valid proxy.
-// Very flaky on windows (crbug.com/518729).
-#if defined(OS_WIN)
-#define MAYBE_PostMessageWithSubframeOnOpenerChain \
-    DISABLED_PostMessageWithSubframeOnOpenerChain
-#else
-#define MAYBE_PostMessageWithSubframeOnOpenerChain \
-    PostMessageWithSubframeOnOpenerChain
-#endif  // defined(OS_WIN)
 IN_PROC_BROWSER_TEST_F(SitePerProcessBrowserTest,
-                       MAYBE_PostMessageWithSubframeOnOpenerChain) {
+                       PostMessageWithSubframeOnOpenerChain) {
   GURL main_url(embedded_test_server()->GetURL(
       "a.com", "/frame_tree/page_with_post_message_frames.html"));
   EXPECT_TRUE(NavigateToURL(shell(), main_url));
 
   // It is safe to obtain the root frame tree node here, as it doesn't change.
   FrameTreeNode* root = static_cast<WebContentsImpl*>(shell()->web_contents())
                             ->GetFrameTree()
                             ->root();
 
   ASSERT_EQ(2U, root->child_count());
@@ skipping 408 matching lines @@
       foo_root->render_manager()->GetRenderFrameProxyHost(site_instance_a));
 
   // Verify that the a.com popup can now find the "foo" popup by name.
   GURL named_frame_url(embedded_test_server()->GetURL("c.com", "/title2.html"));
   NavigateNamedFrame(a_com_shell->web_contents(), named_frame_url, "foo");
   EXPECT_TRUE(WaitForLoadStop(foo_shell->web_contents()));
   EXPECT_EQ(named_frame_url, foo_root->current_url());
 }
 
 }  // namespace content