Move ReadFileToString to the base namespace.

net/test/cert_test_util.cc

Index: net/test/cert_test_util.cc
diff --git a/net/test/cert_test_util.cc b/net/test/cert_test_util.cc
index 085a4594c7636f47b5a885542dae589f2912dfea..5ec07749d508f5758cce834cbf4fd6d0679550c5 100644
--- a/net/test/cert_test_util.cc
+++ b/net/test/cert_test_util.cc
@@ -19,7 +19,7 @@ CertificateList CreateCertificateListFromFile(
     int format) {
   base::FilePath cert_path = certs_dir.AppendASCII(cert_file);
   std::string cert_data;
-  if (!file_util::ReadFileToString(cert_path, &cert_data))
+  if (!base::ReadFileToString(cert_path, &cert_data))
     return CertificateList();
   return X509Certificate::CreateCertificateListFromBytes(cert_data.data(),
                                                          cert_data.size(),
@@ -31,7 +31,7 @@ scoped_refptr<X509Certificate> ImportCertFromFile(
     const std::string& cert_file) {
   base::FilePath cert_path = certs_dir.AppendASCII(cert_file);
   std::string cert_data;
-  if (!file_util::ReadFileToString(cert_path, &cert_data))
+  if (!base::ReadFileToString(cert_path, &cert_data))
     return NULL;
 
   CertificateList certs_in_file =