Assert that ComputedStyleBase is only templated with ComputedStyle

This patch adds a static_assert to assert at compile time that a
ComputedStyleBase can only be templated with a ComputedStyle.

Diff: https://gist.github.com/nainar/ea6c15963c9fe91a4d0c8c9cc5eddbad/revisions

BUG=710938

Review-Url: https://codereview.chromium.org/2896233002
Cr-Commit-Position: refs/heads/master@{#474146}
1 file changed