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

chrome/common/extensions/extension_messages.h

 // 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.
 
 // IPC messages for extensions.
 // Multiply-included message file, hence no include guard.
 
 #include "base/shared_memory.h"
 #include "base/values.h"
 #include "chrome/common/extensions/extension.h"
@@ skipping 200 matching lines @@
 IPC_MESSAGE_ROUTED1(ExtensionMsg_NotifyRenderViewType,
                     ViewType::Type /* view_type */)
 
 // Messages sent from the renderer to the browser.
 
 // A renderer sends this message when an extension process starts an API
 // request. The browser will always respond with a ExtensionMsg_Response.
 IPC_MESSAGE_ROUTED1(ExtensionHostMsg_Request,
                     ExtensionHostMsg_Request_Params)
 
+// A renderer sends this message when an extension process starts an API
+// request. The browser will always respond with a ExtensionMsg_Response.
+IPC_MESSAGE_CONTROL2(ExtensionHostMsg_RequestForIOThread,
+                     int /* routing_id */,
+                     ExtensionHostMsg_Request_Params)
+
 // Notify the browser that the given extension added a listener to an event.
 IPC_MESSAGE_CONTROL2(ExtensionHostMsg_AddListener,
                      std::string /* extension_id */,
                      std::string /* name */)
 
 // Notify the browser that the given extension removed a listener from an
 // event.
 IPC_MESSAGE_CONTROL2(ExtensionHostMsg_RemoveListener,
                      std::string /* extension_id */,
                      std::string /* name */)
@@ skipping 40 matching lines @@
                     bool /* whether the script ran successfully */,
                     std::string /* error message */)
 
 IPC_MESSAGE_ROUTED2(ExtensionHostMsg_DidGetApplicationInfo,
                     int32 /* page_id */,
                     WebApplicationInfo)
 
 // Sent by the renderer to implement chrome.app.installApplication().
 IPC_MESSAGE_ROUTED1(ExtensionHostMsg_InstallApplication,
                     WebApplicationInfo)