chromium: Fix build of beta and dev channels.

Okay, now this time we really broke beta and dev, because python_arch no
longer is in build/common.gypi anymore.

This just adds chrome/chrome_tests.gypi to the list of files to be
changed by sed.

Also, this time I did test at least whether gyp is running fine and
interrupted after the first 1000 build targets, so all channels *should*
now build fine.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>