Move ReadFileToString to the base namespace.

net/test/spawned_test_server/remote_test_server.cc

Index: net/test/spawned_test_server/remote_test_server.cc
diff --git a/net/test/spawned_test_server/remote_test_server.cc b/net/test/spawned_test_server/remote_test_server.cc
index a3b4ef3fdf5549be93210b72b2d709d0c15a0830..594c5d488b480a717472259a860989ebeb5bfe89 100644
--- a/net/test/spawned_test_server/remote_test_server.cc
+++ b/net/test/spawned_test_server/remote_test_server.cc
@@ -169,8 +169,7 @@ bool RemoteTestServer::Init(const base::FilePath& document_root) {
 
   // Parse file to extract the ports information.
   std::string port_info;
-  if (!file_util::ReadFileToString(GetTestServerPortInfoFile(),
-                                   &port_info) ||
+  if (!base::ReadFileToString(GetTestServerPortInfoFile(), &port_info) ||
       port_info.empty()) {
     return false;
   }