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

git-svn-id: e7e1075985beda50ea81ac4472467b4f6e91fc78@548 78cadc50-ecff-11dd-a971-7dbc132099af

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