Avoid doing Inherit recalc on ShadowRoots when they resetStyleInheritance

We don't need to recalc the descendants of ShadowRoot when an ancestor
has an inheritance change if the ShadowRoot has resetStyleInheritance set.

BUG=329720

Review URL: https://codereview.chromium.org/114803006

git-svn-id: svn://svn.chromium.org/blink/trunk@164137 bbb929c8-8fbe-4397-9dbb-9b2b20218538