[DevTools] Rework DevToolsSession interaction with domain handlers.

content/browser/devtools/protocol/dom_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_DOM_HANDLER_H_
 #define CONTENT_BROWSER_DEVTOOLS_PROTOCOL_DOM_HANDLER_H_
 
 #include "base/macros.h"
+#include "content/browser/devtools/protocol/devtools_domain_handler.h"
 #include "content/browser/devtools/protocol/dom.h"
 
 namespace content {
 
 class RenderFrameHostImpl;
 
 namespace protocol {
 
-class DOMHandler : public DOM::Backend {
+class DOMHandler : public DevToolsDomainHandler,
+                   public DOM::Backend {
  public:
   DOMHandler();
   ~DOMHandler() override;
 
-  void Wire(UberDispatcher*);
-  void SetRenderFrameHost(RenderFrameHostImpl* host);
+  void Wire(UberDispatcher* dispatcher) override;
+  void SetRenderFrameHost(RenderFrameHostImpl* host) override;
   Response Disable() override;
 
   Response SetFileInputFiles(
       DOM::NodeId node_id,
       std::unique_ptr<protocol::Array<std::string>> files) override;
 
  private:
   RenderFrameHostImpl* host_;
   DISALLOW_COPY_AND_ASSIGN(DOMHandler);
 };
 
 }  // namespace protocol
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DEVTOOLS_PROTOCOL_DOM_HANDLER_H_