Do not restart the matched properties cache timer if active
https://bugs.webkit.org/show_bug.cgi?id=108345

Reviewed by Andreas Kling.

StyleResolver::addToMatchedPropertiesCache() keeps resetting the timer as more than
matchedDeclarationCacheAdditionsBetweenSweeps entries are added. When armed, we should let
the timer expire at its scheduled time - otherwise it may never get a chance to fire if
entries keep getting added.

No new tests. This is a long lived timer (1min) which makes testing impractical.

* css/StyleResolver.cpp:
(WebCore::StyleResolver::addToMatchedPropertiesCache):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141280 268f45cc-cd09-0410-ab3c-d52691b4dbfc