Generate nonproperty 'explicitInheritance' in ComputedStyleBase.

Move the nonproperty field 'explicitInheritance' to be generated in
ComputedStyleBase. Also moved getter / setter methods to be generated in
ComputedStyleBase.

Note that this renames m_explicitInheritance to something much longer.
This shouldn't affect anything since the member is private and only used
within the generated class.

Also, after this patch, ComputedStyle returns to its original size.

BUG=628043

Review-Url: https://codereview.chromium.org/2672703002
Cr-Commit-Position: refs/heads/master@{#454520}
3 files changed