Remove the concept of 'nonproperties' from ComputedStyle generator.

When we generate ComputedStyle, we differentiate between properties
(which are meant to correspond to CSS properties) and nonproperties
(everything else). However, this terminology is confusing:

- Some nonproperties are derived from real CSS properties (e.g.
  hasSimpleUnderline).
- The generator code contains a lot of "for property_ in nonproperties"
  which is quite confusing.
- The name does not reveal the actual difference between properties
  and nonproperties in terms of code generation.

This patch removes the field role of 'nonproperty' in favour of the
parameter 'has_custom_compare_and_copy'. So there are only two field
roles: 'property' (which includes flags like 'unique' and 'emptyState')
and 'inherited_flag'.

BUG=628043

Review-Url: https://codereview.chromium.org/2830983003
Cr-Commit-Position: refs/heads/master@{#468279}
3 files changed