GitLab

Renamed the Field attribute 'type' to 'storage_type' in
make_computed_style_base.py and the ComputedStyleBase template files.

This is pre-work for when Fields can have both an internal storage and
external type (new attribute 'external_type'), and these types need to
be distinguished without being confusing.

BUG=628043

Review-Url: https://codereview.chromium.org/2563853002
Cr-Commit-Position: refs/heads/master@{#438022}