Revert of Fix scroll chaining for non-descendants of root scroller.

Revert of Fix scroll chaining for non-descendants of root scroller. (patchset #4 id:60001 of https://codereview.chromium.org/2365793002/ )

Reason for revert:
Broke WebView scrolling. See crbug.com/651515

Original issue's description:
> Fix scroll chaining for non-descendants of root scroller.
>
> This CL fixes the scroll chaining behavior for elements that aren't descendants
> of the root scroller element. This can only happen in the non-document root
> scroller proposal.
>
> On the main thread scrolling path, we were previously assuming that all scrolls
> would chain through the effective root scroller. This CL fixes the terminating
> condition as well as removes an invalid DCHECK.
>
> On the compositor side, the chaining mechanisms would previously use the inner
> viewport scroll layer to designate viewport scrolling. Further on, we would
> explicitly check for the inner viewport layer and scroll using cc::Viewport.
> When scrolling a non-descendant of the root scroller, we chain up to the inner
> viewport scroll layer without going through the outer viewport. Scrolling
> cc::Viewport causes scrolling in the outer viewport though so we would scroll
> it inadvertaintly.  I've made changes so that we use the outer viewport to
> designate cc::Viewport scrolling. Scrolls will terminate at the outer viewport
> scroll layer, but they don't have to chain through it.
>
> Unrelated, but I also removed LayerImpl::ApplyScroll as it's unused.
>
> BUG=505516
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel
>
> Committed: https://crrev.com/bc48cb30d9e473b693dc996b7750510d05d50f69
> Cr-Commit-Position: refs/heads/master@{#420763}

TBR=aelias@chromium.org,jaydasika@chromium.org,tdresser@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=505516
Committed: https://crrev.com/29bd015dd8bff8eb77bbd687b7135e45061c021f
Cr-Commit-Position: refs/heads/master@{#422152}

[bokan, 2016-09-30 16:05:01]

The CQ bit was checked by bokan@chromium.org

[bokan, 2016-09-30 16:05:01]

Created Revert of Fix scroll chaining for non-descendants of root scroller.

[commit-bot: I haz the power, 2016-09-30 16:05:20]

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, 2016-09-30 18:04:03]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-30 18:05:54]

Description was changed from

==========
Revert of Fix scroll chaining for non-descendants of root scroller. (patchset #4
id:60001 of https://codereview.chromium.org/2365793002/ )

Reason for revert:
Broke WebView scrolling. See crbug.com/651515

Original issue's description:
> Fix scroll chaining for non-descendants of root scroller.
> 
> This CL fixes the scroll chaining behavior for elements that aren't
descendants
> of the root scroller element. This can only happen in the non-document root
> scroller proposal.
> 
> On the main thread scrolling path, we were previously assuming that all
scrolls
> would chain through the effective root scroller. This CL fixes the terminating
> condition as well as removes an invalid DCHECK.
> 
> On the compositor side, the chaining mechanisms would previously use the inner
> viewport scroll layer to designate viewport scrolling. Further on, we would
> explicitly check for the inner viewport layer and scroll using cc::Viewport.
> When scrolling a non-descendant of the root scroller, we chain up to the inner
> viewport scroll layer without going through the outer viewport. Scrolling
> cc::Viewport causes scrolling in the outer viewport though so we would scroll
> it inadvertaintly.  I've made changes so that we use the outer viewport to
> designate cc::Viewport scrolling. Scrolls will terminate at the outer viewport
> scroll layer, but they don't have to chain through it.
> 
> Unrelated, but I also removed LayerImpl::ApplyScroll as it's unused.
> 
> BUG=505516
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel
> 
> Committed: https://crrev.com/bc48cb30d9e473b693dc996b7750510d05d50f69
> Cr-Commit-Position: refs/heads/master@{#420763}

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

to

==========
Revert of Fix scroll chaining for non-descendants of root scroller. (patchset #4
id:60001 of https://codereview.chromium.org/2365793002/ )

Reason for revert:
Broke WebView scrolling. See crbug.com/651515

Original issue's description:
> Fix scroll chaining for non-descendants of root scroller.
>
> This CL fixes the scroll chaining behavior for elements that aren't
descendants
> of the root scroller element. This can only happen in the non-document root
> scroller proposal.
>
> On the main thread scrolling path, we were previously assuming that all
scrolls
> would chain through the effective root scroller. This CL fixes the terminating
> condition as well as removes an invalid DCHECK.
>
> On the compositor side, the chaining mechanisms would previously use the inner
> viewport scroll layer to designate viewport scrolling. Further on, we would
> explicitly check for the inner viewport layer and scroll using cc::Viewport.
> When scrolling a non-descendant of the root scroller, we chain up to the inner
> viewport scroll layer without going through the outer viewport. Scrolling
> cc::Viewport causes scrolling in the outer viewport though so we would scroll
> it inadvertaintly.  I've made changes so that we use the outer viewport to
> designate cc::Viewport scrolling. Scrolls will terminate at the outer viewport
> scroll layer, but they don't have to chain through it.
>
> Unrelated, but I also removed LayerImpl::ApplyScroll as it's unused.
>
> BUG=505516
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel
>
> Committed: https://crrev.com/bc48cb30d9e473b693dc996b7750510d05d50f69
> Cr-Commit-Position: refs/heads/master@{#420763}

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

Committed: https://crrev.com/29bd015dd8bff8eb77bbd687b7135e45061c021f
Cr-Commit-Position: refs/heads/master@{#422152}
==========

[commit-bot: I haz the power, 2016-09-30 18:05:55]

Patchset 1 (id:??) landed as
https://crrev.com/29bd015dd8bff8eb77bbd687b7135e45061c021f
Cr-Commit-Position: refs/heads/master@{#422152}