Add a couple of files to the exclusion list

These feed into the build system so that they need to trigger a
recompile.

This isn't ideal, but good enough until I get more general diff'ing in
place.

BUG=398118
TEST=none
R=thakis@chromium.org

Review URL: https://codereview.chromium.org/420413003

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@286096 4ff67af0-8c30-449e-8e8b-ad334ec8d88c