Revert of New PaintController under-invalidation checking (patchset #7 id:120001 of https://codereview.chromium.org/2114653003/ )

Reason for revert:
NOTREACHED being hit in checkUnderInvalidation on WebKit Win7 (dbg); see https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win7%20%28dbg%29/builds/6481.

Original issue's description:
> New PaintController under-invalidation checking
>
> This is a follow-up of https://codereview.chromium.org/2107103002/
> which broke the original under-invalidation checking in
> PaintController.
>
> BUG=596983,510908
>
> Committed: https://crrev.com/63b12484f2c59ba177a21aba09b8a4edd38e6ea1
> Cr-Commit-Position: refs/heads/master@{#405805}

TBR=chrishtr@chromium.org,pdr@chromium.org,wangxianzhu@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=596983,510908

Review-Url: https://codereview.chromium.org/2156053002
Cr-Commit-Position: refs/heads/master@{#405988}
7 files changed