StyleResolver should update RuleSets lazily.

This is a fixing patch for preformance regression caused by r159957.
Before applying r159957, removing a style element (or modifying a style element's textcontent)
destroys StyleResolver, e.g. style.textContent = '';

After applying r159957, we don't need to destroy StyleResolver.
The r159957 makes us to avoid FullStyleRecalc and full RuleSet re-creation (document,
and shadow trees).

But the patch caused Parser/css-parser-yui.html's performance regression.
Because firstly the performance test destroys StyleResolver and skip StyleResolver::appendAuthorStyleSheets.
(If we have no StyleResolver, we don't need to update RuleSet, StyleInvalidationAnalysis, and so on)

So we should update RuleSets lazily. This solution improves Parser/css-parser-yui.html's performance again.

BUG=305885,308796
TEST=all existing tests should pass.

Review URL: https://codereview.chromium.org/42543007

git-svn-id: svn://svn.chromium.org/blink/trunk@162187 bbb929c8-8fbe-4397-9dbb-9b2b20218538