Fix chromium.gyp_env to see GYP_MSVS_VERSION.

Fix from scottmg.

R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/136663004

git-svn-id: http://src.chromium.org/svn/trunk/src/build@244585 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

gyp_helper.py

@@ -34,6 +34,7 @@ def apply_gyp_environment_from_file(file_path):
       'GYP_CROSSCOMPILE',
       'GYP_GENERATOR_OUTPUT',
       'GYP_GENERATORS',
+      'GYP_MSVS_VERSION',
   )
   for var in supported_vars:
     file_val = file_data.get(var)