Move ReadFileToString to the base namespace.

chrome/browser/extensions/extension_action_icon_factory_unittest.cc

Index: chrome/browser/extensions/extension_action_icon_factory_unittest.cc
diff --git a/chrome/browser/extensions/extension_action_icon_factory_unittest.cc b/chrome/browser/extensions/extension_action_icon_factory_unittest.cc
index 39ea0d6d45a1db447f687c94962e78175724d57e..3eadffa27e60c5b5c184fc40f98a02c3ac4f1d76 100644
--- a/chrome/browser/extensions/extension_action_icon_factory_unittest.cc
+++ b/chrome/browser/extensions/extension_action_icon_factory_unittest.cc
@@ -70,7 +70,7 @@ gfx::Image LoadIcon(const std::string& filename) {
   path = path.AppendASCII("extensions/api_test").AppendASCII(filename);
 
   std::string file_contents;
-  file_util::ReadFileToString(path, &file_contents);
+  base::ReadFileToString(path, &file_contents);
   const unsigned char* data =
       reinterpret_cast<const unsigned char*>(file_contents.data());