GitLab

This patch moves:
  - build/scripts/make_cssom_types.py ->
    build/scripts/core/css/make_cssom_types.py

  - build/scripts/templates/CSSOMTypes.cpp.tmpl ->
    build/scripts/core/css/templates/CSSOMTypes.cpp.tmpl

  - build/scripts/templates/CSSOMKeywords.cpp.tmpl ->
    build/scripts/core/css/templates/CSSOMKeywords.cpp.tmpl

We append 'build/scripts' to the system path in
make_cssom_types.py so that it can import modules such as
json5_generator.

We also add a new GN template "code_generator" to be used by
the new style generators. There are some additional changes
to make the linter happy.

This patch does not change behaviour.

Bug: 732657
Change-Id: I07bb1042cf548ef8795a04833f8224ad1ffe232c
Reviewed-on: https://chromium-review.googlesource.com/558587
Commit-Queue: Darren Shen <shend@chromium.org>
Reviewed-by: meade_UTC10 <meade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487349}