DevTools: complete 2-sided migration to attach w/ id (content)

content/renderer/devtools/devtools_agent.cc

Index: content/renderer/devtools/devtools_agent.cc
diff --git a/content/renderer/devtools/devtools_agent.cc b/content/renderer/devtools/devtools_agent.cc
index c10a7909ba7a496bec68db81c6bb4f4d89baea00..5ba456b8b1445619a1af433d00c14ccff3345af8 100644
--- a/content/renderer/devtools/devtools_agent.cc
+++ b/content/renderer/devtools/devtools_agent.cc
@@ -121,10 +121,6 @@ void DevToolsAgent::sendMessageToInspectorFrontend(
                                                          message.utf8()));
 }
 
-int DevToolsAgent::hostIdentifier() {
-  return routing_id();
-}
-
 int DevToolsAgent::debuggerId() {
   return routing_id();
 }