Return first_run_win to using the Chrome path provider to look up the user data dir.

chrome/browser/first_run/first_run_internal.h

Index: chrome/browser/first_run/first_run_internal.h
diff --git a/chrome/browser/first_run/first_run_internal.h b/chrome/browser/first_run/first_run_internal.h
index 3e32db294969cdb3df018fb1e43d2da078f145f4..c139f70ee2abe2ef31dc99e152ee8e9731ab87d2 100644
--- a/chrome/browser/first_run/first_run_internal.h
+++ b/chrome/browser/first_run/first_run_internal.h
@@ -38,9 +38,6 @@ enum FirstRunState {
 // This variable should only be accessed through IsChromeFirstRun().
 extern FirstRunState first_run_;
 
-// The kSentinelFile file absence will tell us it is a first run.
-extern const char* const kSentinelFile;
-
 // Loads master preferences from the master preference file into the installer
 // master preferences. Passes the master preference file path out in
 // master_prefs_path. Returns the pointer to installer::MasterPreferences object