Store new ComputedStyle object if style did not change.

The comparison of ComputedStyle does not take additional flags into
account. For instance, the AffectedBy* flags used for updating pseudo
classes like :hover. We used to call SetStyleInternal, but this was
removed because the previous comment said it was because of style
sharing which is now removed.

The display:contents case (768406) never worked because the code path
for StoreNonLayoutObjectComputedStyle() was always skipped when
computed style compared to be equal.

Bug: 768406, 767832
Change-Id: Iac4708e3cd3a6451d99c1bb2bb69efb74289b8eb
Reviewed-on: https://chromium-review.googlesource.com/681755
Reviewed-by: nainar <nainar@chromium.org>
Commit-Queue: Rune Lillesveen <rune@opera.com>
Cr-Commit-Position: refs/heads/master@{#504285}
2 files changed