Move more string_util functions to base namespace.

tools/gn/filesystem_utils.cc

 // Copyright (c) 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 "tools/gn/filesystem_utils.h"
 
 #include <algorithm>
 
 #include "base/files/file_util.h"
 #include "base/logging.h"
@@ skipping 82 matching lines @@
 
 bool DoesBeginWindowsDriveLetter(const base::StringPiece& path) {
   if (path.size() < 3)
     return false;
 
   // Check colon first, this will generally fail fastest.
   if (path[1] != ':')
     return false;
 
   // Check drive letter.
-  if (!IsAsciiAlpha(path[0]))
+  if (!base::IsAsciiAlpha(path[0]))
     return false;
 
   if (!IsSlash(path[2]))
     return false;
   return true;
 }
 #endif
 
 // A wrapper around FilePath.GetComponents that works the way we need. This is
 // not super efficient since it does some O(n) transformations on the path. If
@@ skipping 699 matching lines @@
 
 SourceDir GetCurrentOutputDir(const Scope* scope) {
   return GetOutputDirForSourceDirAsOutputFile(
       scope->settings(), scope->GetSourceDir()).AsSourceDir(
           scope->settings()->build_settings());
 }
 
 SourceDir GetCurrentGenDir(const Scope* scope) {
   return GetGenDirForSourceDir(scope->settings(), scope->GetSourceDir());
 }