[DevTools] Migrate from AgentStateCallbacks to DevToolsAgentHostObserver.

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/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "content/browser/devtools/devtools_agent_host_impl.h"
@@ skipping 27 matching lines @@
   DevToolsManager* manager = DevToolsManager::GetInstance();
   manager->SetHttpHandler(nullptr);
 }
 
 // static
 DevToolsManager* DevToolsManager::GetInstance() {
   return base::Singleton<DevToolsManager>::get();
 }
 
 DevToolsManager::DevToolsManager()
-    : delegate_(GetContentClient()->browser()->GetDevToolsManagerDelegate()),
-      attached_hosts_count_(0) {
+    : delegate_(GetContentClient()->browser()->GetDevToolsManagerDelegate()) {
 }
 
 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,
-                     GetContentClient()->browser()->GetNetLog()));
-    }
-    ++attached_hosts_count_;
-  } else {
-    --attached_hosts_count_;
-    if (!attached_hosts_count_) {
-      BrowserThread::PostTask(
-          BrowserThread::IO,
-          FROM_HERE,
-          base::Bind(&NetLogObserver::Detach));
-    }
-  }
 }
 
 void DevToolsManager::SetHttpHandler(
     std::unique_ptr<DevToolsHttpHandler> http_handler) {
   http_handler_ = std::move(http_handler);
 }
 
 }  // namespace content