Generate StyleRareNonInheritedData in ComputedStyleBase.

This patch generates the fields stored directly on
StyleRareNonInheritedData. This group is special in that it has nested
subgroups such as StyleWillChangeData and StyleTransformData.

Important changes to note:

- name_utilities.py: split_name is changed to consider "3D" as one word
  instead of two. This is so that the name for transform-style-3D is
  formatted correctly.

- CSSProperties.json5: Added new pointer types std::unique_ptr and
  DataPersistent. Added DataRef temporarily as a valid pointer type so
  that the fields for nested groups like StyleWillChangeData can be
  generated, without generating the nested group itself. This is to
  keep the CL small. DataRef will be removed as a valid pointer type
  once all the subgroups are generated.

- DataPersistent.h: Added move assignment so that the internal move
  setter for DataPersistent fields can be generated.

- group.tmpl: Comparisons are not generated for a few fields. See
  https://www.diffchecker.com/u0H0SvNe for which fields are not
  compared. This change makes groups ignore these fields when
  generating operator==.

This patch does not change behaviour.

Diff of generated files:
https://gist.github.com/781ba773a43594145ee79cfa270614d6/revisions

BUG=628043

Review-Url: https://codereview.chromium.org/2923333002
Cr-Commit-Position: refs/heads/master@{#479146}
12 files changed