[DevTools] Rework DevToolsSession interaction with domain handlers.

content/browser/devtools/protocol/emulation_handler.cc

 // Copyright 2015 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/protocol/emulation_handler.h"
 
 #include <utility>
 
 #include "base/strings/string_number_conversions.h"
 #include "build/build_config.h"
@@ skipping 37 matching lines @@
   if (protocol_value ==
       Emulation::SetTouchEmulationEnabled::ConfigurationEnum::Desktop) {
     result = ui::GestureProviderConfigType::GENERIC_DESKTOP;
   }
   return result;
 }
 
 }  // namespace
 
 EmulationHandler::EmulationHandler()
-    : touch_emulation_enabled_(false),
+    : DevToolsDomainHandler(Emulation::Metainfo::domainName),
+      touch_emulation_enabled_(false),
       device_emulation_enabled_(false),
       host_(nullptr) {
 }
 
 EmulationHandler::~EmulationHandler() {
 }
 
 void EmulationHandler::SetRenderFrameHost(RenderFrameHostImpl* host) {
   if (host_ == host)
     return;
@@ skipping 209 matching lines @@
     widget_host->Send(new ViewMsg_EnableDeviceEmulation(
         widget_host->GetRoutingID(), device_emulation_params_));
   } else {
     widget_host->Send(new ViewMsg_DisableDeviceEmulation(
         widget_host->GetRoutingID()));
   }
 }
 
 }  // namespace protocol
 }  // namespace content