Move PathExists to base namespace.

chrome/installer/util/master_preferences.cc

Index: chrome/installer/util/master_preferences.cc
diff --git a/chrome/installer/util/master_preferences.cc b/chrome/installer/util/master_preferences.cc
index 6e8a94fb17e627533495ee8f20ad639a2b86d404..d345e95c63c6cf3db3b218d6f19ff3e463b348ea 100644
--- a/chrome/installer/util/master_preferences.cc
+++ b/chrome/installer/util/master_preferences.cc
@@ -101,7 +101,7 @@ MasterPreferences::MasterPreferences(const base::FilePath& prefs_path)
   // Failure to read the file is ignored as |json_data| will be the empty string
   // and the remainder of this MasterPreferences object should still be
   // initialized as best as possible.
-  if (file_util::PathExists(prefs_path) &&
+  if (base::PathExists(prefs_path) &&
       !file_util::ReadFileToString(prefs_path, &json_data)) {
     LOG(ERROR) << "Failed to read preferences from " << prefs_path.value();
   }