[DevTools] Rework DevToolsSession interaction with domain handlers.

content/browser/devtools/protocol/system_info_handler.h

 // 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.
 
 #ifndef CONTENT_BROWSER_DEVTOOLS_PROTOCOL_SYSTEM_INFO_HANDLER_H_
 #define CONTENT_BROWSER_DEVTOOLS_PROTOCOL_SYSTEM_INFO_HANDLER_H_
 
 #include <set>
 
 #include "base/macros.h"
+#include "content/browser/devtools/protocol/devtools_domain_handler.h"
 #include "content/browser/devtools/protocol/system_info.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/gpu_data_manager_observer.h"
 
 namespace content {
 namespace protocol {
 
-class SystemInfoHandler : public SystemInfo::Backend {
+class SystemInfoHandler : public DevToolsDomainHandler,
+                          public SystemInfo::Backend {
  public:
 
   SystemInfoHandler();
   ~SystemInfoHandler() override;
 
-  void Wire(UberDispatcher*);
-  Response Disable() override;
+  void Wire(UberDispatcher* dispatcher) override;
 
   void GetInfo(std::unique_ptr<GetInfoCallback> callback) override;
 
  private:
   friend class SystemInfoHandlerGpuObserver;
 
   DISALLOW_COPY_AND_ASSIGN(SystemInfoHandler);
 };
 
 }  // namespace protocol
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DEVTOOLS_PROTOCOL_SYSTEM_INFO_HANDLER_H_