Revert of Fix slow repaint object registration

Revert of Fix slow repaint object registration (patchset #2 id:20001 of https://codereview.chromium.org/1240443003/)

Reason for revert:
Speculative revert: appears to have broken Linux MSAN bots.

http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20MSAN/builds/4413


Original issue's description:
> Fix slow repaint object registration
> 
> The LayoutView now paints background, so the special condition to accelerate
> frame scrolling with fixed root background should be updated as well.
> 
> As a drive-by fix, this CL also corrects slow repaint object accounting so
> we no longer leak slow repaint object count.
> 
> BUG=506002
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198894

TBR=vollick@chromium.org,trchen@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=506002
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=198913

[Noel Gordon, 2015-07-15 03:03:56]

Created Revert of Fix slow repaint object registration

[commit-bot: I haz the power, 2015-07-15 03:04:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1224083019/1

[commit-bot: I haz the power, 2015-07-15 03:04:37]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=198913

[Noel Gordon, 2015-07-15 03:14:10]

noel@chromium.org changed reviewers:
+ rtoy@chromium.org

[Noel Gordon, 2015-07-15 03:16:36]

noel@chromium.org changed reviewers:
+ yosin@chromium.org

[Noel Gordon, 2015-07-15 04:22:51]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1234153003/ by noel@chromium.org.

The reason for reverting is: This patch was not the cause, relanding..