Avoid using BrowserThread and ContentBrowserClient in NetLogObserver.

content/browser/devtools/devtools_manager.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/devtools/devtools_manager.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "content/browser/devtools/devtools_agent_host_impl.h"
 #include "content/browser/loader/netlog_observer.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/content_browser_client.h"
 
 namespace content {
 
 // static
 DevToolsManager* DevToolsManager::GetInstance() {
   return base::Singleton<DevToolsManager>::get();
 }
 
 DevToolsManager::DevToolsManager()
     : delegate_(GetContentClient()->browser()->GetDevToolsManagerDelegate()),
       attached_hosts_count_(0) {
+  // Pass the IO thread task runner to the NetLogObserver class.
+  NetLogObserver::SetIOThreadTaskRunner(

[pfeldman, 2016/07/06 18:36:14]

It is unclear why netlog observer is initialized with the thread from the
devtools manager. The scope of netlog is greater than the one of the manager.

[ananta, 2016/07/08 14:11:02]

Passed it via Attach instead.

+      BrowserThread::GetMessageLoopProxyForThread(BrowserThread::IO));
 }
 
 DevToolsManager::~DevToolsManager() {
   DCHECK(!attached_hosts_count_);
 }
 
 void DevToolsManager::AgentHostStateChanged(
     DevToolsAgentHostImpl* agent_host, bool attached) {
   if (attached) {
     if (!attached_hosts_count_) {
       BrowserThread::PostTask(
           BrowserThread::IO,
           FROM_HERE,
-          base::Bind(&NetLogObserver::Attach));
+          base::Bind(&NetLogObserver::Attach,
+                     GetContentClient()->browser()->GetNetLog()));
     }
     ++attached_hosts_count_;
   } else {
     --attached_hosts_count_;
     if (!attached_hosts_count_) {
       BrowserThread::PostTask(
           BrowserThread::IO,
           FROM_HERE,
           base::Bind(&NetLogObserver::Detach));
     }
   }
 }
 
 }  // namespace content