Do not keep InvalidationSets on the Oilpan heap.
An InvalidationSet keeps sets of names/strings and tend to have lifetimes
that track those of RuleFeatureSets and not be shared.
Hence it doesn't meet the bar for being on the Oilpan heap; for workloads
where invalidations happen frequently, having them on the heap just causes
unnecessary follow-on work in having to sweep out at some later GC.
Trivially tidy up StyleResolver construction as part of this CL also.
R=haraken
BUG=
Review URL: https://codereview.chromium.org/1389333003
Cr-Commit-Position: refs/heads/master@{#352829}
12 files changed
