[DevTools] Rework DevToolsSession interaction with domain handlers.

content/browser/devtools/forwarding_agent_host.cc

Index: content/browser/devtools/forwarding_agent_host.cc
diff --git a/content/browser/devtools/forwarding_agent_host.cc b/content/browser/devtools/forwarding_agent_host.cc
index 98b89545dc99587abf6c3e9bdf58599db3b5a24e..808759dea90b35574f08d749390ec1167058db28 100644
--- a/content/browser/devtools/forwarding_agent_host.cc
+++ b/content/browser/devtools/forwarding_agent_host.cc
@@ -26,18 +26,19 @@ void ForwardingAgentHost::DispatchOnClientHost(const std::string& message) {
 }
 
 void ForwardingAgentHost::ConnectionClosed() {
-  HostClosed();
+  ForceDetach(false);
 }
 
-void ForwardingAgentHost::Attach() {
+void ForwardingAgentHost::AttachSession(DevToolsSession* session) {
   delegate_->Attach(this);
 }
 
-void ForwardingAgentHost::Detach() {
+void ForwardingAgentHost::DetachSession(int session_id) {
   delegate_->Detach();
 }
 
 bool ForwardingAgentHost::DispatchProtocolMessage(
+    DevToolsSession* session,
     const std::string& message) {
   delegate_->SendMessageToBackend(message);
   return true;