[DevTools] Rework DevToolsSession interaction with domain handlers.

content/browser/devtools/forwarding_agent_host.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_FORWARDING_AGENT_HOST_H_
 #define CONTENT_BROWSER_DEVTOOLS_FORWARDING_AGENT_HOST_H_
 
 #include <memory>
 
 #include "base/memory/ref_counted.h"
@@ skipping 12 matching lines @@
       std::unique_ptr<DevToolsExternalAgentProxyDelegate> delegate);
 
  private:
   ~ForwardingAgentHost() override;
 
   // DevToolsExternalAgentProxy implementation.
   void DispatchOnClientHost(const std::string& message) override;
   void ConnectionClosed() override;
 
   // DevToolsAgentHostImpl implementation.
-  void Attach() override;
-  void Detach() override;
-  bool DispatchProtocolMessage(const std::string& message) override;
+  void AttachSession(DevToolsSession* session) override;
+  void DetachSession(int session_id) override;
+  bool DispatchProtocolMessage(
+      DevToolsSession* session,
+      const std::string& message) override;
 
   // DevToolsAgentHost implementation
   std::string GetType() override;
   std::string GetTitle() override;
   GURL GetURL() override;
   GURL GetFaviconURL() override;
   std::string GetFrontendURL() override;
   bool Activate() override;
   void Reload() override;
   bool Close() override;
 
   std::unique_ptr<DevToolsExternalAgentProxyDelegate> delegate_;
   std::string type_;
   std::string title_;
   GURL url_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DEVTOOLS_FORWARDING_AGENT_HOST_H_