DevTools: prepare workers for DevToolsManager::Attach(Detach)ClientHost removal.

content/browser/devtools/devtools_manager_impl.cc

Index: content/browser/devtools/devtools_manager_impl.cc
diff --git a/content/browser/devtools/devtools_manager_impl.cc b/content/browser/devtools/devtools_manager_impl.cc
index a5a72e4a02c076c2e83d491712a4e2f107316574..c15e5f2b77620c32ace982bed170d7d7f55c352e 100644
--- a/content/browser/devtools/devtools_manager_impl.cc
+++ b/content/browser/devtools/devtools_manager_impl.cc
@@ -241,9 +241,12 @@ void DevToolsManagerImpl::UnbindClientHost(DevToolsAgentHost* agent_host,
         FROM_HERE,
         base::Bind(&DevToolsNetLogObserver::Detach));
   }
+  int process_id = agent_host->GetRenderProcessId();
+
+  // Lazy agent hosts can be deleted from within detach.
+  // Do not access agent_host below this line.
   agent_host->Detach();
 
-  int process_id = agent_host->GetRenderProcessId();
   if (process_id == -1)
     return;
   for (AgentToClientHostMap::iterator it = agent_to_client_host_.begin();