Generate StyleRareInheritedData in ComputedStyleBase.

This patch generates StyleRareInheritedData in ComputedStyleBase. Because some
fields are stored as smart pointers, we have to introduce a new parameter
in the JSON file called "pointer_type_name", which is the name of the
smart pointer type. As with the handwritten code, pointer fields are
compared using DataEquivalent, not ==.

All fields are generated as storage_only in this patch, but future patches
may change that.

Diff of generated files:
https://gist.github.com/darrnshn/4ffa0198d36f4e0ff56ee0fc3b12619a/revisions

BUG=628043

Review-Url: https://codereview.chromium.org/2887333003
Cr-Commit-Position: refs/heads/master@{#474510}
8 files changed