Revert of Don't expand empty rect during rect mapping (patchset #4 id:60001 of https://codereview.c…

Revert of Don't expand empty rect during rect mapping (patchset #4 id:60001 of https://codereview.chromium.org/2416693002/ )

Reason for revert:
It changed
  transform->mapRect(enclosingIntRect(rect))
to
  transform->mapRect(FloatRect(enclosingIntRect(rect)))
causing missing enclosingIntRect() after the transform.

We may also need enclosingIntRect for empty rects because even empty
object can have visible filter depending on pixel snapping here.

BUG=669774
TEST=paint/invalidation/rotated-subpixel.html

Original issue's description:
> Don't expand empty rect during rect mapping
>
> For example, enclosingIntRect(LayoutRect(0.5, 0.5, 0, 0)) results
> IntRect(0, 0, 1, 1). This causes unnecessary non-empty visual rects
> mapped from empty LayoutRects.
>
> This CL is mainly to reduce the difference between the old path and
> slimmingPaintInvalidation with pixel snapping feature.
>
> Committed: https://crrev.com/67c516aaed2486295a98d7f0ff2235b921cd7933
> Cr-Commit-Position: refs/heads/master@{#424970}

TBR=chrishtr@chromium.org

Review-Url: https://codereview.chromium.org/2545573002
Cr-Commit-Position: refs/heads/master@{#435677}

[Xianzhu, 2016-12-02 19:01:12]

Committed patchset #1 (id:1) to pending queue manually as
232175eb6bdfa080b36e59a1a9ed419eef9849b5.