Move ReadFileToString to the base namespace.

chrome/browser/sessions/better_session_restore_browsertest.cc

Index: chrome/browser/sessions/better_session_restore_browsertest.cc
diff --git a/chrome/browser/sessions/better_session_restore_browsertest.cc b/chrome/browser/sessions/better_session_restore_browsertest.cc
index 999197bf8d2296a57f2bccd5382a6007647bfe56..77d4bd888921ef5e8cb8730516a76bfe8072f759 100644
--- a/chrome/browser/sessions/better_session_restore_browsertest.cc
+++ b/chrome/browser/sessions/better_session_restore_browsertest.cc
@@ -127,7 +127,7 @@ class BetterSessionRestoreTest : public InProcessBrowserTest {
          it != test_files.end(); ++it) {
       base::FilePath path = test_file_dir.AppendASCII(*it);
       std::string contents;
-      CHECK(file_util::ReadFileToString(path, &contents));
+      CHECK(base::ReadFileToString(path, &contents));
       g_file_contents.Get()["/" + test_path_ + *it] = contents;
       net::URLRequestFilter::GetInstance()->AddUrlHandler(
           GURL(fake_server_address_ + test_path_ + *it),