Revert of cc: Make PaintedScrollbarLayer not use ContentsScalingLayer

Revert of cc: Make PaintedScrollbarLayer not use ContentsScalingLayer (patchset #4 id:60001 of https://codereview.chromium.org/913133004/)

Reason for revert:
Causes DCHECKs in layout tests.

Original issue's description:
> cc: Make PaintedScrollbarLayer not use ContentsScalingLayer
>
> ContentsScalingLayer depends on the main thread running calculate draw
> properties and updating contents scale and content bounds.  In order to
> switch to using property trees (which don't currently calculate these
> values), PaintedScrollbarLayer needs to calculate contents scale
> internally.
>
> This also moves towards removing ContentsScalingLayer (currently also
> used by TiledLayer and HeadsUpDisplayLayer), which once it's gone will
> allow contents scale and content bounds to removed entirely from Layer
> and LayerImpl.
>
> Committed: https://crrev.com/a499bbb66f29815ae0cef3eaa62ee2b3d3526d04
> Cr-Commit-Position: refs/heads/master@{#316088}

TBR=danakj@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/8e7bf2757ee8f82a7d2bd5a50c68812db3398420
Cr-Commit-Position: refs/heads/master@{#316089}

[enne (OOO), 2015-02-12 23:55:27]

Created Revert of cc: Make PaintedScrollbarLayer not use ContentsScalingLayer

[commit-bot: I haz the power, 2015-02-12 23:56:43]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/913393004/1

[commit-bot: I haz the power, 2015-02-12 23:58:09]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-12 23:59:02]

Patchset 1 (id:??) landed as
https://crrev.com/8e7bf2757ee8f82a7d2bd5a50c68812db3398420
Cr-Commit-Position: refs/heads/master@{#316089}