PlzNavigate: fix flaky TabManagerTest.TabManagerBasics browser test.

content/browser/web_contents/web_contents_impl.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/web_contents/web_contents_impl.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <utility>
@@ skipping 656 matching lines @@
 
 bool WebContentsImpl::OnMessageReceived(RenderViewHost* render_view_host,
                                         const IPC::Message& message) {
   return OnMessageReceived(render_view_host, NULL, message);
 }
 
 bool WebContentsImpl::OnMessageReceived(RenderViewHost* render_view_host,
                                         RenderFrameHost* render_frame_host,
                                         const IPC::Message& message) {
   DCHECK(render_view_host || render_frame_host);
-  if (GetWebUI() &&
-      static_cast<WebUIImpl*>(GetWebUI())->OnMessageReceived(message)) {
-    return true;
+
+  if (render_view_host) {
+    RenderFrameHost* main_frame = render_view_host->GetMainFrame();
+    if (main_frame) {

[jam, 2016/12/08 17:43:53]

nit: are you sure you need this check?

[yzshen1, 2016/12/08 17:46:19]

Yes, there are cases where render_view_host->GetMainFrame() returns null. I
didn't look deeper to see whether those are expected though. Do you think it is
a bug?

Thanks! 

+      WebUIImpl* web_ui =
+          static_cast<RenderFrameHostImpl*>(main_frame)->web_ui();
+      if (web_ui && web_ui->OnMessageReceived(message))
+        return true;
+    }
   }
 
   if (render_frame_host) {
     for (auto& observer : observers_) {
       if (observer.OnMessageReceived(message, render_frame_host))
         return true;
     }
   } else {
     for (auto& observer : observers_) {
       if (observer.OnMessageReceived(message))
@@ skipping 4586 matching lines @@
   dialog_manager_ = dialog_manager;
 }
 
 void WebContentsImpl::RemoveBindingSet(const std::string& interface_name) {
   auto it = binding_sets_.find(interface_name);
   if (it != binding_sets_.end())
     binding_sets_.erase(it);
 }
 
 }  // namespace content