Move ReadFileToString to the base namespace.

chrome/test/chromedriver/chrome_launcher.cc

Index: chrome/test/chromedriver/chrome_launcher.cc
diff --git a/chrome/test/chromedriver/chrome_launcher.cc b/chrome/test/chromedriver/chrome_launcher.cc
index c9b0e4905498fa990e784c7fac4fc5c350f153d0..58fff91ad1536989fba192b497c8da2eec4737b4 100644
--- a/chrome/test/chromedriver/chrome_launcher.cc
+++ b/chrome/test/chromedriver/chrome_launcher.cc
@@ -472,7 +472,7 @@ Status ProcessExtension(const std::string& extension,
   // Parse the manifest and set the 'key' if not already present.
   base::FilePath manifest_path(extension_dir.AppendASCII("manifest.json"));
   std::string manifest_data;
-  if (!file_util::ReadFileToString(manifest_path, &manifest_data))
+  if (!base::ReadFileToString(manifest_path, &manifest_data))
     return Status(kUnknownError, "cannot read manifest");
   scoped_ptr<base::Value> manifest_value(base::JSONReader::Read(manifest_data));
   base::DictionaryValue* manifest;