Remove redundant DevToolsManager methods and clean up its clients.

chrome/browser/extensions/api/debugger/debugger_api.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.
 
 // Implements the Chrome Extensions Debugger API.
 
 #include "chrome/browser/extensions/api/debugger/debugger_api.h"
 
 #include <map>
 #include <set>
@@ skipping 507 matching lines @@
   if (!webkit_glue::IsInspectorProtocolVersionSupported(
       params->required_version)) {
     error_ = ErrorUtils::FormatErrorMessage(
         keys::kProtocolVersionNotSupportedError,
         params->required_version);
     return false;
   }
 
   scoped_refptr<DevToolsAgentHost> agent(DevToolsAgentHost::GetOrCreateFor(
       contents_->GetRenderViewHost()));
-  DevToolsClientHost* client_host = DevToolsManager::GetInstance()->
-      GetDevToolsClientHostFor(agent);
-
-  if (client_host != NULL) {
+  if (agent->IsAttached()) {
     FormatErrorMessage(keys::kAlreadyAttachedError);
     return false;
   }
 
   new ExtensionDevToolsClientHost(contents_,
                                   GetExtension()->id(),
                                   GetExtension()->name(),
                                   debuggee_);
   SendResponse(true);
   return true;
@@ skipping 43 matching lines @@
   }
 
   DictionaryValue* result_body;
   SendCommand::Results::Result result;
   if (response->GetDictionary("result", &result_body))
     result.additional_properties.Swap(result_body);
 
   results_ = SendCommand::Results::Create(result);
   SendResponse(true);
 }