Use a valid /prefetch argument when launching a process.

chrome/app/chrome_watcher_command_line_win.cc

 // Copyright (c) 2014 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/app/chrome_watcher_command_line_win.h"
 
 #include <stdint.h>
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "base/win/win_util.h"
 #include "chrome/common/chrome_switches.h"
+#include "components/startup_metric_utils/common/pre_read_field_trial_utils_win.h"
 #include "content/public/common/content_switches.h"
 
 namespace {
 
 const char kMainThreadIdSwitch[] = "main-thread-id";
 const char kOnIninitializedEventHandleSwitch[] = "on-initialized-event-handle";
 const char kParentHandleSwitch[] = "parent-handle";
 
 void AppendHandleSwitch(const std::string& switch_name,
                         HANDLE handle,
@@ skipping 119 matching lines @@
     DWORD main_thread_id,
     HANDLE on_initialized_event) {
   base::CommandLine command_line(chrome_exe);
   command_line.AppendSwitchASCII(switches::kProcessType,
                                  switches::kWatcherProcess);
   command_line.AppendSwitchASCII(kMainThreadIdSwitch,
                                  base::UintToString(main_thread_id));
   AppendHandleSwitch(kOnIninitializedEventHandleSwitch, on_initialized_event,
                      &command_line);
   AppendHandleSwitch(kParentHandleSwitch, parent_process, &command_line);
+
+#if defined(OS_WIN)
+  if (startup_metric_utils::GetPreReadOptions().prefetch_argument)
+    command_line.AppendArg(switches::kPrefetchArgumentWatcher);
+#endif  // defined(OS_WIN)
+
   return command_line;
 }
 
 bool InterpretChromeWatcherCommandLine(
     const base::CommandLine& command_line,
     base::win::ScopedHandle* parent_process,
     DWORD* main_thread_id,
     base::win::ScopedHandle* on_initialized_event) {
   DCHECK(on_initialized_event);
   DCHECK(parent_process);
@@ skipping 38 matching lines @@
       !parent_process->IsValid()) {
     // If one was valid and not the other, free the valid one.
     on_initialized_event->Close();
     parent_process->Close();
     *main_thread_id = 0;
     return false;
   }
 
   return true;
 }