Change Windows build default to build with VS 2010.

tools/gyp_dart.py

 #!/usr/bin/env python
 
 # Copyright (c) 2012 The Dart Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 Invoke gyp to generate build files for building the Dart VM.
 """
 
 import os
 import subprocess
 import sys
 
 def execute(args):
   process = subprocess.Popen(args)
   process.wait()
   return process.returncode
 
 def main():
   args = ['python', 'dart/third_party/gyp/gyp', '--depth=dart',
           '-Idart/tools/gyp/all.gypi', 'dart/dart.gyp']
 
   if sys.platform == 'win32':
-    # Generate Visual Studio 2008 compatible files by default.
+    # Generate Visual Studio 2010 compatible files by default.
     if not os.environ.get('GYP_MSVS_VERSION'):
-      args.extend(['-G', 'msvs_version=2008'])
+      args.extend(['-G', 'msvs_version=2010'])
 
   sys.exit(execute(args))
 
 if __name__ == '__main__':
   main()