Make a pre-read A/B field-trial

chrome/browser/browser_main_win.h

Index: chrome/browser/browser_main_win.h
===================================================================
--- chrome/browser/browser_main_win.h	(revision 95298)
+++ chrome/browser/browser_main_win.h	(working copy)
@@ -37,4 +37,11 @@
 // 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_