html_viewer: Add DevToolsAgentImpl.

components/devtools_service/public/interfaces/devtools_service.mojom

 // 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.
 
 module devtools_service;
 
 // The DevTools service exposes two interfaces:
 // - DevToolsCoordinator: Privileged interface used by the shell to setup the
 //   service and perform other control operations. Other applications are not
 //   able to request this interface.
@@ skipping 12 matching lines @@
 interface DevToolsRegistry {
   // Registers a DevTools agent.
   RegisterAgent(DevToolsAgent agent);
 };
 
 interface DevToolsAgent {
   // Sets/resets a client to receive event notifications and responses for
   // DispatchProtocolMessage() calls. If a client doesn't want to receive
   // messages anymore, it could simply close the underlying message pipe of
   // |client|.
-  SetClient(DevToolsAgentClient client);
+  SetClient(DevToolsAgentClient client, string client_id);
 
   // Sends a command (in remote debugging protocol JSON format) to the agent.
   DispatchProtocolMessage(string message);
 };
 
 interface DevToolsAgentClient {
   // Sends a notification or response message (in remote debugging protocol JSON
   // format) to the client.
   DispatchProtocolMessage(string message);
 };