[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..025b00ade506f8c410f508730e1e6e9a915471b8 100644
--- a/content/browser/devtools/forwarding_agent_host.cc
+++ b/content/browser/devtools/forwarding_agent_host.cc
@@ -29,15 +29,16 @@ void ForwardingAgentHost::ConnectionClosed() {
   HostClosed();
 }
 
-void ForwardingAgentHost::Attach() {
+void ForwardingAgentHost::Attach(DevToolsSession* session) {
   delegate_->Attach(this);
 }
 
-void ForwardingAgentHost::Detach() {
+void ForwardingAgentHost::Detach(DevToolsSession* session) {
   delegate_->Detach();
 }
 
 bool ForwardingAgentHost::DispatchProtocolMessage(
+    DevToolsSession* session,
     const std::string& message) {
   delegate_->SendMessageToBackend(message);
   return true;