Remove task.h and finish base::Bind() migration.

chrome/browser/platform_util_chromeos.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/browser/platform_util.h"
 
 #include "base/bind.h"
+#include "base/callback.h"
 #include "base/file_util.h"
-#include "base/task.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/extensions/file_manager_util.h"
 #include "chrome/browser/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "content/public/browser/browser_thread.h"
 #include "googleurl/src/gurl.h"
 
 using content::BrowserThread;
 
@@ skipping 67 matching lines @@
 void OpenExternal(const GURL& url) {
   if (url.SchemeIs("mailto")) {
     std::string string_url = kGmailComposeUrl;
     string_url.append(url.spec());
     BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                             base::Bind(OpenURL, string_url));
   }
 }
 
 }  // namespace platform_util