Made CSS white-space property use IndependentInherit, which is part
of the process of making property inheritance faster. This change
adds 1 bit to the size of ComputedStyle but significantly reduces the
time for a recalc for independent-only changes involving whitespace.

Tested using:
third_party/WebKit/LayoutTests/fast/css/invalidation/independent-inheritance-fast-path.html

BUG=622138

Review-Url: https://codereview.chromium.org/2538983002
Cr-Commit-Position: refs/heads/master@{#435559}