Use invalidation sets for :read-only and :read-write.

Gets rid of SubtreeStyleChange which relies on sibling tree recalcs.

R=tkent@chromium.org,ericwilligers@chromium.org
BUG=557440

Review URL: https://codereview.chromium.org/1454003002

Cr-Commit-Position: refs/heads/master@{#360298}
void RuleFeatureSet::FeatureMetadata::clear()
{
    usesFirstLineRules = false;
    usesWindowInactiveSelector = false;
    foundSiblingSelector = false;
    maxDirectAdjacentSelectors = 0;
}

void RuleFeatureSet::FeatureMetadata::clear()
{
    usesFirstLineRules = false;
    usesWindowInactiveSelector = false;
    foundSiblingSelector = false;
    maxDirectAdjacentSelectors = 0;
}
