Add an accessor to HeadlessBrowser for the IO thread

headless/public/headless_browser.h

 // Copyright 2015 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.
 
 #ifndef HEADLESS_PUBLIC_HEADLESS_BROWSER_H_
 #define HEADLESS_PUBLIC_HEADLESS_BROWSER_H_
 
 #include <memory>
 #include <string>
 #include <unordered_map>
@@ skipping 37 matching lines @@
   // Returns the HeadlessWebContents associated with the
   // |devtools_agent_host_id| if any.  Otherwise returns null.
   virtual HeadlessWebContents* GetWebContentsForDevToolsAgentHostId(
       const std::string& devtools_agent_host_id) = 0;
 
   // Returns HeadlessBrowserContext associated with the given id if any.
   // Otherwise returns null.
   virtual HeadlessBrowserContext* GetBrowserContextForId(
       const std::string& id) = 0;
 
+  // Returns a task runner for submitting work to the browser file thread.
+  virtual scoped_refptr<base::SingleThreadTaskRunner> BrowserFileThread()
+      const = 0;
+
+  // Returns a task runner for submitting work to the browser io thread.
+  virtual scoped_refptr<base::SingleThreadTaskRunner> BrowserIOThread()
+      const = 0;
+
   // Returns a task runner for submitting work to the browser main thread.
   virtual scoped_refptr<base::SingleThreadTaskRunner> BrowserMainThread()
       const = 0;
 
-  // Returns a task runner for submitting work to the browser file thread.
-  virtual scoped_refptr<base::SingleThreadTaskRunner> BrowserFileThread()
-      const = 0;
-
   // Requests browser to stop as soon as possible. |Run| will return as soon as
   // browser stops.
   // IMPORTANT: All pointers to HeadlessBrowserContexts and HeadlessWebContents
   // become invalid after calling this function.
   virtual void Shutdown() = 0;
 
  protected:
   HeadlessBrowser() {}
   virtual ~HeadlessBrowser() {}
 
@@ skipping 124 matching lines @@
 // the main loop, it will only return after HeadlessBrowser::Shutdown() is
 // called, returning the exit code for the process. It is not possible to
 // initialize the browser again after it has been torn down.
 int HeadlessBrowserMain(
     HeadlessBrowser::Options options,
     const base::Callback<void(HeadlessBrowser*)>& on_browser_start_callback);
 
 }  // namespace headless
 
 #endif  // HEADLESS_PUBLIC_HEADLESS_BROWSER_H_