Fix front-end host creation upon navigation

content/browser/devtools/devtools_frontend_host_impl.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 "content/browser/devtools/devtools_frontend_host_impl.h"
 
 #include <stddef.h>
 
 #include "content/browser/bad_message.h"
+#include "content/browser/frame_host/frame_tree.h"
+#include "content/browser/web_contents/web_contents_impl.h"
 #include "content/common/devtools_messages.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/content_client.h"
 #include "grit/devtools_resources_map.h"
 
 namespace content {
 
 namespace {
 const char kCompatibilityScript[] = "devtools_compatibility.js";
 const char kCompatibilityScriptSourceURL[] =
     "\n//# "
     "sourceURL=chrome-devtools://devtools/bundled/devtools_compatibility.js";
 }
 
 // static
 DevToolsFrontendHost* DevToolsFrontendHost::Create(
-    RenderFrameHost* frontend_main_frame,
+    WebContents* web_contents,
     const HandleMessageCallback& handle_message_callback) {
-  return new DevToolsFrontendHostImpl(frontend_main_frame,
+  RenderFrameHost* frame = web_contents->GetMainFrame();
+  FrameTree* tree = static_cast<WebContentsImpl*>(web_contents)->GetFrameTree();
+  RenderFrameHostManager* rfhm = tree->root()->render_manager();
+  RenderFrameHost* pending_frame = rfhm->pending_frame_host();
+  return new DevToolsFrontendHostImpl(pending_frame ? pending_frame : frame,

[pfeldman, 2017/01/10 22:31:51]

This looks fragile and implementation implies navigation is racy. Can we always
use pending host from the call site?

                                       handle_message_callback);
 }
 
 // static
 base::StringPiece DevToolsFrontendHost::GetFrontendResource(
     const std::string& path) {
   for (size_t i = 0; i < kDevtoolsResourcesSize; ++i) {
     if (path == kDevtoolsResources[i].name) {
       return GetContentClient()->GetDataResource(
           kDevtoolsResources[i].value, ui::SCALE_FACTOR_NONE);
@@ skipping 36 matching lines @@
   IPC_END_MESSAGE_MAP()
   return handled;
 }
 
 void DevToolsFrontendHostImpl::OnDispatchOnEmbedder(
     const std::string& message) {
   handle_message_callback_.Run(message);
 }
 
 }  // namespace content