Update build utils to prefer Visual Studio 2013.

tools/utils.py

 # 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.
 
 # This file contains a set of utilities functions used by other Python-based
 # scripts.
 
 import commands
 import datetime
 import json
@@ skipping 79 matching lines @@
   # We need to know whether host is 64-bit so that we are looking in right
   # registry for Visual Studio path.
   if sys.maxsize > 2**32 or win32process.IsWow64Process():
     wow6432Node = 'Wow6432Node\\'
   else:
     wow6432Node = ''
   return r'SOFTWARE\%s%s' % (wow6432Node, name)
 
 # Try to guess Visual Studio location when buiding on Windows.
 def GuessVisualStudioPath():
-  defaultPath = r"C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7" \
+  defaultPath = r"C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7" \
                 r"\IDE"
   defaultExecutable = "devenv.com"
 
   if not IsWindows():
     return defaultPath, defaultExecutable
 
   keyNamesAndExecutables = [
     # Pair for non-Express editions.
     (GetWindowsRegistryKeyName(r'Microsoft\VisualStudio'), 'devenv.com'),
     # Pair for 2012 Express edition.
@@ skipping 24 matching lines @@
         match = re.match(r'^\d+\.\d+$', subkeyName)
         if match:
           with _winreg.OpenKey(key, subkeyName) as subkey:
             try:
               (installDir, registrytype) = _winreg.QueryValueEx(subkey,
                                                                 'InstallDir')
             except WindowsError:
               # Can't find value under the key - continue to the next key.
               continue
             isExpress = executable != 'devenv.com'
-            if not isExpress and subkeyName == '10.0':
-              # Stop search since if we found non-Express VS2010 version
+            if not isExpress and subkeyName == '12.0':
+              # Stop search since if we found non-Express VS2013 version
               # installed, which is preferred version.
               return installDir, executable
             else:
               version = float(subkeyName)
               # We prefer higher version of Visual Studio and given equal
               # version numbers we prefer non-Express edition.
               if version > bestGuess[0]:
                 bestGuess = (version, (installDir, executable))
     finally:
       _winreg.CloseKey(key)
@@ skipping 456 matching lines @@
     os.chdir(self._working_directory)
 
   def __exit__(self, *_):
     print "Enter directory = ", self._old_cwd
     os.chdir(self._old_cwd)
 
 
 if __name__ == "__main__":
   import sys
   Main()