[dart:io] Move Platform.ansiSupported to {Stdin,Stdout}.supportsAnsiEscapes

runtime/bin/platform_macos.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(HOST_OS_MACOS)
 
 #include "bin/platform.h"
 
 #if !HOST_OS_IOS
@@ skipping 136 matching lines @@
   char* path = DartUtils::ScopedCString(path_size);
   if (_NSGetExecutablePath(path, &path_size) != 0) {
     return NULL;
   }
   // Return the canonical path as the returned path might contain symlinks.
   const char* canon_path = File::GetCanonicalPath(path);
   return canon_path;
 }
 
 
-bool Platform::AnsiSupported() {
-  return true;
-}
-
-
 void Platform::Exit(int exit_code) {
   exit(exit_code);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(HOST_OS_MACOS)