Move code from from ComputedStyleBase.cpp.tmpl to .h.tmpl

This patch moves code from ComputedStyleBase.cpp.tmpl to the h.tmpl
file in preparation to make it a template so that we can make
ComputedStyle a templated argument and access both functions on
ComputedStyleBase and ComputedStyle in the base class.

Diff: https://gist.github.com/nainar/f7cb9953674378504ac6795be365bb1f/revisions

BUG=710938

Review-Url: https://codereview.chromium.org/2875233002
Cr-Commit-Position: refs/heads/master@{#471664}
4 files changed