Support being invoked without any file and check an env var and then fall back to a canned default. Review URL: http://codereview.chromium.org/155519
Support being invoked without any file and check an env var and then fall back to a canned default.
Review URL: http://codereview.chromium.org/155519
witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp