Add internal move setter for storage_only fields in ComputedStyle

This patch adds a protected rvalue reference setter for storage_only
fields in ComputedStyle. This will allow handwritten setters to take
advantage of move semantics (e.g. Length fields, pointer fields).

Diff of generated files:
https://gist.github.com/b5c155dcd25ab8a89259e1b33f5ece0b/revisions

BUG=628043

Review-Url: https://codereview.chromium.org/2885333002
Cr-Commit-Position: refs/heads/master@{#472736}
1 file changed