Use a valid /prefetch argument when launching a process.

chrome/browser/browser_process_impl.cc

 // Copyright (c) 2012 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/browser_process_impl.h"
 
 #include <stddef.h>
 #include <algorithm>
 #include <map>
 #include <utility>
@@ skipping 93 matching lines @@
 #include "content/public/common/content_switches.h"
 #include "extensions/common/constants.h"
 #include "net/socket/client_socket_pool_manager.h"
 #include "net/url_request/url_request_context_getter.h"
 #include "ui/base/idle/idle.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/message_center/message_center.h"
 
 #if defined(OS_WIN)
 #include "base/win/windows_version.h"
+#include "components/startup_metric_utils/common/pre_read_field_trial_utils_win.h"
 #include "ui/views/focus/view_storage.h"
 #elif defined(OS_MACOSX)
 #include "chrome/browser/chrome_browser_main_mac.h"
 #endif
 
 #if !defined(OS_ANDROID)
 #include "chrome/browser/ui/user_manager.h"
 #include "components/gcm_driver/gcm_client_factory.h"
 #include "components/gcm_driver/gcm_desktop_utils.h"
 #endif
@@ skipping 1137 matching lines @@
         new_cl->AppendSwitch(i->first);
       }
   }
 
   // Ensure that our desired switches are set on the new process.
   for (size_t i = 0; i < arraysize(kSwitchesToAddOnAutorestart); ++i) {
     if (!new_cl->HasSwitch(kSwitchesToAddOnAutorestart[i]))
       new_cl->AppendSwitch(kSwitchesToAddOnAutorestart[i]);
   }
 
+#if defined(OS_WIN)
+  if (startup_metric_utils::GetPreReadOptions().prefetch_argument)
+    new_cl->AppendArg(switches::kPrefetchArgumentBrowserBackground);
+#endif  // defined(OS_WIN)
+
   DLOG(WARNING) << "Shutting down current instance of the browser.";
   chrome::AttemptExit();
 
   // Transfer ownership to Upgrade.
   upgrade_util::SetNewCommandLine(new_cl.release());
 }
 
 void BrowserProcessImpl::OnAutoupdateTimer() {
   if (CanAutorestartForUpdate()) {
     DLOG(WARNING) << "Detected update.  Restarting browser.";
     RestartBackgroundInstance();
   }
 }
 
 #endif  // (defined(OS_WIN) || defined(OS_LINUX)) && !defined(OS_CHROMEOS)