Revert of Split RootScrollerController into top-document and child-document classes

Revert of Split RootScrollerController into top-document and child-document classes (patchset #3 id:40001 of https://codereview.chromium.org/2280453002/ )

Reason for revert:
Causes oopif renderers to die. See https://crbug.com/641775

Original issue's description:
> Split RootScrollerController into top-document and child-document classes
> 
> Work on making RootScrollerController work across iframes revealed that there's
> two responsibilities that need management. All frames need a
> RootScrollerController to manage the Element currently set as root scroller and
> determine which Element should eventually become the effective root scroller.
> In addition, we need the RootScrollerController to manage the
> ViewportApplyScroll and set it on the appropriate element. Since only one
> Element on the whole page needs this callback set, it makes sense that only the
> top document should have this responsibility. Experience with classes like
> FrameView and EventHandler shows that this may be better served by subclassing
> the top level object rather than having isMainFrame() checks intermingled with
> the other code.
> 
> BUG=505516
> 
> Committed: https://crrev.com/f8bc5669c399f88dc57d6a8832bc233db306c3c7
> Cr-Commit-Position: refs/heads/master@{#414796}

TBR=tdresser@chromium.org,bokan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=505516

[lfg, 2016-08-30 14:06:47]

The CQ bit was checked by lfg@chromium.org

[lfg, 2016-08-30 14:06:48]

Created Revert of Split RootScrollerController into top-document and
child-document classes

[commit-bot: I haz the power, 2016-08-30 14:07:03]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-30 14:09:37]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-30 14:09:39]

Try jobs failed on following builders:
  mac_chromium_compile_dbg_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)
  mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[lfg, 2016-08-30 14:35:54]

Description was changed from

==========
Revert of Split RootScrollerController into top-document and child-document
classes (patchset #3 id:40001 of https://codereview.chromium.org/2280453002/ )

Reason for revert:
Causes oopif renderers to die. See https://crbug.com/641775

Original issue's description:
> Split RootScrollerController into top-document and child-document classes
> 
> Work on making RootScrollerController work across iframes revealed that
there's
> two responsibilities that need management. All frames need a
> RootScrollerController to manage the Element currently set as root scroller
and
> determine which Element should eventually become the effective root scroller.
> In addition, we need the RootScrollerController to manage the
> ViewportApplyScroll and set it on the appropriate element. Since only one
> Element on the whole page needs this callback set, it makes sense that only
the
> top document should have this responsibility. Experience with classes like
> FrameView and EventHandler shows that this may be better served by subclassing
> the top level object rather than having isMainFrame() checks intermingled with
> the other code.
> 
> BUG=505516
> 
> Committed: https://crrev.com/f8bc5669c399f88dc57d6a8832bc233db306c3c7
> Cr-Commit-Position: refs/heads/master@{#414796}

TBR=tdresser@chromium.org,bokan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=505516
==========

to

==========
Revert of Split RootScrollerController into top-document and child-document
classes (patchset #3 id:40001 of https://codereview.chromium.org/2280453002/ )

Reason for revert:
Causes oopif renderers to die. See https://crbug.com/641775

Original issue's description:
> Split RootScrollerController into top-document and child-document classes
> 
> Work on making RootScrollerController work across iframes revealed that
there's
> two responsibilities that need management. All frames need a
> RootScrollerController to manage the Element currently set as root scroller
and
> determine which Element should eventually become the effective root scroller.
> In addition, we need the RootScrollerController to manage the
> ViewportApplyScroll and set it on the appropriate element. Since only one
> Element on the whole page needs this callback set, it makes sense that only
the
> top document should have this responsibility. Experience with classes like
> FrameView and EventHandler shows that this may be better served by subclassing
> the top level object rather than having isMainFrame() checks intermingled with
> the other code.
> 
> BUG=505516
> 
> Committed: https://crrev.com/f8bc5669c399f88dc57d6a8832bc233db306c3c7
> Cr-Commit-Position: refs/heads/master@{#414796}

TBR=tdresser@chromium.org,bokan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=505516
==========

[lfg, 2016-08-30 14:37:15]

On 2016/08/30 14:09:39, commit-bot: I haz the power wrote:
> Try jobs failed on following builders:
>   mac_chromium_compile_dbg_ng on master.tryserver.chromium.mac (JOB_FAILED,
>
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)
>   mac_chromium_rel_ng on master.tryserver.chromium.mac (JOB_FAILED,
>
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

The revert does not apply cleanly anymore, since this is not on the M54 branch,
let's just try to fix the bug.