DevTools: provide an option to return traces as streams

content/browser/devtools/browser_devtools_agent_host.cc

Index: content/browser/devtools/browser_devtools_agent_host.cc
diff --git a/content/browser/devtools/browser_devtools_agent_host.cc b/content/browser/devtools/browser_devtools_agent_host.cc
index e7dbaa60098095004a5e85df64d6306249d4c435..ce3b45d715af0ec7c381d161e579202cc68dd96a 100644
--- a/content/browser/devtools/browser_devtools_agent_host.cc
+++ b/content/browser/devtools/browser_devtools_agent_host.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "content/browser/devtools/devtools_protocol_handler.h"
+#include "content/browser/devtools/protocol/io_handler.h"
 #include "content/browser/devtools/protocol/system_info_handler.h"
 #include "content/browser/devtools/protocol/tethering_handler.h"
 #include "content/browser/devtools/protocol/tracing_handler.h"
@@ -21,12 +22,13 @@ scoped_refptr<DevToolsAgentHost> DevToolsAgentHost::CreateForBrowser(
 BrowserDevToolsAgentHost::BrowserDevToolsAgentHost(
     scoped_refptr<base::SingleThreadTaskRunner> tethering_task_runner,
     const CreateServerSocketCallback& socket_callback)
-    : system_info_handler_(new devtools::system_info::SystemInfoHandler()),
+    : io_handler_(new devtools::io::IOHandler(GetIOContext())),
+      system_info_handler_(new devtools::system_info::SystemInfoHandler()),
       tethering_handler_(
           new devtools::tethering::TetheringHandler(socket_callback,
                                                     tethering_task_runner)),
       tracing_handler_(new devtools::tracing::TracingHandler(
-          devtools::tracing::TracingHandler::Browser)),
+          devtools::tracing::TracingHandler::Browser, GetIOContext())),
       protocol_handler_(new DevToolsProtocolHandler(
           this,
           base::Bind(&BrowserDevToolsAgentHost::SendMessageToClient,