Enable compiling with automatically-downloaded VS toolchain on Windows bots

make.py

 # Copyright 2011 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # "Makefile" replacement to build skia for Windows.
 # More info at https://sites.google.com/site/skiadocs/
 #
 # Some usage examples:
 #   make clean
@@ skipping 35 matching lines @@
     print '> %s' % command
     if os.system(command):
         sys.exit(1)
 
 def MakeClean():
     """Cross-platform "make clean" operation."""
     cd(SCRIPT_DIR)
     rmtree(OUT_SUBDIR)
 
 
-def CheckWindowsEnvironment():
-    """For Windows: check environment variables needed for command-line build.
-
-    If those environment variables are missing, try to set them.
-    If environment variables can be set up, this function returns; otherwise,
-    it displays an error message and exits.
-    """
-    # If we already have the proper environment variables, nothing to do here.
-    try:
-        env_DevEnvDir = os.environ['DevEnvDir']
-        return  # found it, so we are done
-    except KeyError:
-        pass # go on and run the rest of this function
-
-    print ('\nCould not find Visual Studio environment variables.'
-           '\nPerhaps you have not yet run vcvars32.bat as described at'
-           '\nhttp://msdn.microsoft.com/en-us/library/f2ccy3wt.aspx ?')
-    found_path = None
-    try:
-        possible_path = os.path.abspath(os.path.join(
-            os.environ['VS100COMNTOOLS'], os.path.pardir, os.path.pardir,
-            'VC', 'bin', 'vcvars32.bat'))
-        if os.path.exists(possible_path):
-            found_path = possible_path
-    except KeyError:
-        pass
-    if found_path:
-        print '\nIt looks like you can run that script at:\n%s' % found_path
-    else:
-        print '\nUnable to find vcvars32.bat on your system.'
-    sys.exit(1)
-
-
 def MakeWindows(targets):
     """For Windows: build as appropriate for the command line arguments.
 
     parameters:
         targets: build targets as a list of strings
     """
-    # TODO(epoger): I'm not sure if this is needed for ninja builds.
-    CheckWindowsEnvironment()
-
     # Run gyp_skia to prepare Visual Studio projects.
     cd(SCRIPT_DIR)
     runcommand('python gyp_skia')
 
     # We already built the gypfiles...
     while TARGET_GYP in targets:
         targets.remove(TARGET_GYP)
 
     # And call ninja to do the work!
     if targets:
@@ skipping 55 matching lines @@
         print 'unknown platform (os.name=%s, sys.platform=%s); see %s' % (
             os.name, sys.platform, 'https://sites.google.com/site/skiadocs/')
         sys.exit(1)
     sys.exit(0)
 
 
 # main()
 Make(sys.argv[1:])