Enable support for hard coding Win7.
Enable support for hard coding Win7.

It's not optimal but this is a WIP. Eventually we want target_os to be the right
value but it is not right yet.

R=vadimsh@chromium.org

Review URL: https://codereview.chromium.org/137783026

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@245915 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build