Handle extension webrequest API on the IO thread. This speeds up blocking event

chrome/renderer/extensions/extension_process_bindings.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/extensions/extension_process_bindings.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 398 matching lines @@
     if (!v8_extension->CheckPermissionForCurrentContext(name))
       return v8::Undefined();
 
     GURL source_url;
     WebFrame* webframe = WebFrame::frameForCurrentContext();
     if (webframe)
       source_url = webframe->url();
 
     int request_id = args[2]->Int32Value();
     bool has_callback = args[3]->BooleanValue();
+    bool for_io_thread = args[4]->BooleanValue();
 
     v8::Persistent<v8::Context> current_context =
         v8::Persistent<v8::Context>::New(v8::Context::GetCurrent());
     DCHECK(!current_context.IsEmpty());
     GetPendingRequestMap()[request_id].reset(new PendingRequest(
         current_context, name));
 
     ExtensionHostMsg_Request_Params params;
     params.name = name;
     params.arguments.Swap(value_args);
     params.source_url = source_url;
     params.request_id = request_id;
     params.has_callback = has_callback;
     params.user_gesture = webframe->isProcessingUserGesture();
-    renderview->Send(new ExtensionHostMsg_Request(
-        renderview->routing_id(), params));
+    if (for_io_thread) {
+      renderview->Send(new ExtensionHostMsg_RequestForIOThread(
+          renderview->routing_id(), params));
+    } else {
+      renderview->Send(new ExtensionHostMsg_Request(
+          renderview->routing_id(), params));
+    }
 
     return v8::Undefined();
   }
 
   // Starts an API request to the browser, with an optional callback.  The
   // callback will be dispatched to EventBindings::HandleResponse.
   static v8::Handle<v8::Value> StartRequest(const v8::Arguments& args) {
     std::string str_args = *v8::String::Utf8Value(args[1]);
     base::JSONReader reader;
     scoped_ptr<Value> value_args;
@@ skipping 129 matching lines @@
   if (!retval.IsEmpty() && !retval->IsUndefined()) {
     std::string error = *v8::String::AsciiValue(retval);
     DCHECK(false) << error;
   }
 #endif
 
   request->second->context.Dispose();
   request->second->context.Clear();
   pending_requests.erase(request);
 }