Simplify handling of names in make_computed_style_base.py.

There is a lot of duplicate code in make_computed_style_base.py used to
handle names. This patch refactors the code so that the Field class
handles most of the naming logic.

BUG=628043

Review-Url: https://codereview.chromium.org/2762573005
Cr-Commit-Position: refs/heads/master@{#458906}
1 file changed