Extract debugger target enumeration into a separate class

content/browser/devtools/devtools_agent_host_impl.h

Index: content/browser/devtools/devtools_agent_host_impl.h
diff --git a/content/browser/devtools/devtools_agent_host_impl.h b/content/browser/devtools/devtools_agent_host_impl.h
index c3a52155f91294dd70f9fa3cab7d31f258eeff58..5e9cdfb715a6178475e31c52248eed11c0f713ac 100644
--- a/content/browser/devtools/devtools_agent_host_impl.h
+++ b/content/browser/devtools/devtools_agent_host_impl.h
@@ -41,9 +41,9 @@ class CONTENT_EXPORT DevToolsAgentHostImpl : public DevToolsAgentHost {
     close_listener_ = listener;
   }
 
-  int id() { return id_; }
-
   // DevToolsAgentHost implementation.
+  virtual std::string GetId() OVERRIDE;
+
   virtual RenderViewHost* GetRenderViewHost() OVERRIDE;
 
  protected:
@@ -59,7 +59,7 @@ class CONTENT_EXPORT DevToolsAgentHostImpl : public DevToolsAgentHost {
   CloseListener* close_listener_;
 
  private:
-  int id_;
+  const std::string id_;
 };
 
 }  // namespace content