Rename RareInheritedData::variables and RareNonInheritedData::variables.
When we generate fields in ComputedStyleBase, the name of the fields
must be distinct. Sometimes, existing handwritten data members share
the same name because they are stored on different groups. This may not
be true when they become generated. Hence, we have to rename these
members with a distinct name.
This patch renames:
- StyleRareInheritedData::variables_ -> inherited_variables_
- StyleRareNonInheritedData::variables_ -> non_inherited_variables_
There are no changes in behaviour.