Move StartsWith[ASCII] to base namespace.

chrome/browser/prefetch/prefetch_field_trial.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/prefetch/prefetch_field_trial.h"
 
 #include <string>
 
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_util.h"
 #include "chrome/browser/prerender/prerender_field_trial.h"
 
 namespace prefetch {
 
 bool DisableForFieldTrial() {
   std::string experiment = base::FieldTrialList::FindFullName("Prefetch");
-  return StartsWithASCII(experiment, "ExperimentDisable", false);
+  return base::StartsWithASCII(experiment, "ExperimentDisable", false);
 }
 
 }  // namespace prefetch