[DevTools] Fix frontend host race and assert.

chrome/browser/devtools/devtools_ui_bindings.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 "chrome/browser/devtools/devtools_ui_bindings.h"
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/scoped_user_pref_update.h"
@@ skipping 466 matching lines @@
  return NULL;
 }
 
 DevToolsUIBindings::DevToolsUIBindings(content::WebContents* web_contents)
     : profile_(Profile::FromBrowserContext(web_contents->GetBrowserContext())),
       android_bridge_(DevToolsAndroidBridge::Factory::GetForProfile(profile_)),
       web_contents_(web_contents),
       delegate_(new DefaultBindingsDelegate(web_contents_)),
       devices_updates_enabled_(false),
       frontend_loaded_(false),
+      frontend_reattaching_(false),
       weak_factory_(this) {
   g_instances.Get().push_back(this);
   frontend_contents_observer_.reset(new FrontendWebContentsObserver(this));
   web_contents_->GetMutableRendererPrefs()->can_accept_load_drops = false;
 
   file_helper_.reset(new DevToolsFileHelper(web_contents_, profile_, this));
   file_system_indexer_ = new DevToolsFileSystemIndexer();
   extensions::ChromeExtensionWebContentsObserver::CreateForWebContents(
       web_contents_);
 
@@ skipping 389 matching lines @@
 }
 
 void DevToolsUIBindings::ClearPreferences() {
   DictionaryPrefUpdate update(profile_->GetPrefs(),
                               prefs::kDevToolsPreferences);
   update.Get()->Clear();
 }
 
 void DevToolsUIBindings::DispatchProtocolMessageFromDevToolsFrontend(
     const std::string& message) {
-  if (agent_host_.get())
+  if (agent_host_.get() && !frontend_reattaching_)

[pfeldman, 2015/12/07 21:38:42]

When does this happen and why should it be ignored?

[dgozman, 2015/12/07 21:46:40]

Happens in Reattach. First paragraph of the patch description answers the second
question.

[pfeldman, 2015/12/07 21:48:36]

But how can it be dispatched twice?

[dgozman, 2015/12/07 22:03:53]

Sorry, it wasn't clear. It's not the same message dispatched twice, but one more
similar message. I've updated description.

     agent_host_->DispatchProtocolMessage(message);
 }
 
 void DevToolsUIBindings::RecordEnumeratedHistogram(const std::string& name,
                                                    int sample,
                                                    int boundary_value) {
   if (!(boundary_value >= 0 && boundary_value <= 100 && sample >= 0 &&
         sample < boundary_value)) {
     // TODO(nick): Replace with chrome::bad_message::ReceivedBadMessage().
     frontend_host_->BadMessageRecieved();
@@ skipping 212 matching lines @@
 
 void DevToolsUIBindings::AttachTo(
     const scoped_refptr<content::DevToolsAgentHost>& agent_host) {
   if (agent_host_.get())
     Detach();
   agent_host_ = agent_host;
   agent_host_->AttachClient(this);
 }
 
 void DevToolsUIBindings::Reattach() {
+  frontend_reattaching_ = true;
   DCHECK(agent_host_.get());
   agent_host_->DetachClient();
   agent_host_->AttachClient(this);
 }
 
 void DevToolsUIBindings::Detach() {
   if (agent_host_.get())
     agent_host_->DetachClient();
   agent_host_ = NULL;
 }
@@ skipping 29 matching lines @@
         javascript.append(", ").append(json);
       }
     }
   }
   javascript.append(");");
   web_contents_->GetMainFrame()->ExecuteJavaScript(
       base::UTF8ToUTF16(javascript));
 }
 
 void DevToolsUIBindings::DocumentOnLoadCompletedInMainFrame() {
+  frontend_reattaching_ = false;
   // In the DEBUG_DEVTOOLS mode, the DocumentOnLoadCompletedInMainFrame event
   // arrives before the LoadCompleted event, thus it should not trigger the
   // frontend load handling.
 #if !defined(DEBUG_DEVTOOLS)
   FrontendLoaded();
 #endif
 }
 
 void DevToolsUIBindings::DidNavigateMainFrame() {
   frontend_loaded_ = false;
 }
 
 void DevToolsUIBindings::FrontendLoaded() {
   if (frontend_loaded_)
     return;
   frontend_loaded_ = true;
 
   // Call delegate first - it seeds importants bit of information.
   delegate_->OnLoadCompleted();
 
   AddDevToolsExtensionsToClient();
   if (g_web_socket_api_channel)
     g_web_socket_api_channel->AttachedToBindings(this);
 }