Actually call the NormlizeFilePath function for download platform detection.

This should make Cygwin work to match "win32".

Review URL: https://codereview.chromium.org/108743002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@239244 0039d316-1c4b-4281-b951-d872f2087c98

download_from_google_storage.py

@@ -333,7 +333,7 @@ def main(args):
 
   # Make sure we should run at all based on platform matching.
   if options.platform:
-    if not re.match(options.platform, sys.platform):
+    if not re.match(options.platform, GetNormalizedPlatform()):
       if options.verbose:
         print('The current platform doesn\'t match "%s", skipping.' %
               options.platform)