Add a testing config for Windows 7 32 bit bot.

For now starting with a small number of test:
-browser_tests & nacl_integration tests to exercise the NaCl 32 bit sandbox
-sbox*tests and base_unittests for sandbox code

BUG=579701

Review URL: https://codereview.chromium.org/1620203007

Cr-Commit-Position: refs/heads/master@{#371131}
1 file changed