Add generated InheritedDataShared in ComputedStyleBase.

ComputedStyle::InheritedDataShared is a handwritten function that
compares subgroup pointers. This makes it difficult to change the group
that a field belongs to, as it might break the correctness of the
function.

This patch adds a generated function InheritedDataShared in
ComputedStyleBase that works no matter where fields are stored.

There are no behavioural changes in this patch.

Diff of generated files:
https://gist.github.com/darrnshn/a88dd2eaf35380e4e24d18384fb3c4b4/revisions

BUG=628043

Review-Url: https://codereview.chromium.org/2879123002
Cr-Commit-Position: refs/heads/master@{#472593}
3 files changed