Move ReadFileToString to the 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 d345e95c63c6cf3db3b218d6f19ff3e463b348ea..0895c8326c9d720f0cc74b9c82388c07e19201ed 100644
--- a/chrome/installer/util/master_preferences.cc
+++ b/chrome/installer/util/master_preferences.cc
@@ -102,7 +102,7 @@ MasterPreferences::MasterPreferences(const base::FilePath& prefs_path)
   // and the remainder of this MasterPreferences object should still be
   // initialized as best as possible.
   if (base::PathExists(prefs_path) &&
-      !file_util::ReadFileToString(prefs_path, &json_data)) {
+      !base::ReadFileToString(prefs_path, &json_data)) {
     LOG(ERROR) << "Failed to read preferences from " << prefs_path.value();
   }
   if (InitializeFromString(json_data))