Make a pre-read A/B field-trial

chrome/browser/browser_main_win.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.
 
 // Contains functions used by BrowserMain() that are win32-specific.
 
 #ifndef CHROME_BROWSER_BROWSER_MAIN_WIN_H_
 #define CHROME_BROWSER_BROWSER_MAIN_WIN_H_
 #pragma once
 
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 // HideIconsCommand & ShowIconsCommand. Chrome doesn't support hide icons
 // functionality so we just ask the users if they want to uninstall Chrome.
 int HandleIconsCommands(const CommandLine& parsed_command_line);
 
 // Check if there is any machine level Chrome installed on the current
 // machine. If yes and the current Chrome process is user level, we do not
 // allow the user level Chrome to run. So we notify the user and uninstall
 // user level Chrome.
 bool CheckMachineLevelInstall();
 
+// Records a Startup category value to an UMA histogram in the context of the
+// PreReadExperiment field-trial. This will also report to the appropriate
+// Startup.HistogramName_PreRead(Enabled|Disabled) histogram as appropriate.
+// This is only called from OS_WIN specific code, so the implementation is
+// in browser_main_win.cc. This is a Windows specific experiment.
+void RecordPreReadExperimentTime(const char* name, base::TimeDelta time);
+
 #endif  // CHROME_BROWSER_BROWSER_MAIN_WIN_H_