Revert of Remove PaintInfo's paintingRoot

Revert of Remove PaintInfo's paintingRoot (patchset #5 id:80001 of https://codereview.chromium.org/1602513004/ )

Reason for revert:
Broke oilpan and closed the tree:
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Oilpan%20Builder/builds/673/steps/compile/logs/stdio

I'll fix this tomorrow and reland.

Original issue's description:
> Remove PaintInfo's paintingRoot
>
> PaintInfo had a paintingRoot member for supporting drawing a single
> layout object (including descendants). This complexity is spread
> throughout the painting code and only exists to support drag and drop
> drag images:
> https://chromium.googlesource.com/chromium/src/+/65e7e9d4860e50bb677228f0b83848cce208eb76
>
> This patch switches to directly painting LayoutObjects and removes the
> complex paintingRoot code.
>
> ClusterTelemetry results: 0.5% record time savings:
> https://storage.cloud.google.com/cluster-telemetry/tasks/chromium_perf_runs/pdr-20160118203222/html/index.html
>
> BUG=577004
>
> Committed: https://crrev.com/63c9596d206c896b35ae8a5bff4db73847f62f33
> Cr-Commit-Position: refs/heads/master@{#370334}

TBR=chrishtr@chromium.org,wangxianzhu@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=577004
Committed: https://crrev.com/ce37a6c4442ded2ffd29703b27d77e126528f3f4
Cr-Commit-Position: refs/heads/master@{#370335}

[pdr., 2016-01-20 06:56:08]

Created Revert of Remove PaintInfo's paintingRoot

[commit-bot: I haz the power, 2016-01-20 06:56:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1610063002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1610063002/1

[commit-bot: I haz the power, 2016-01-20 06:58:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-20 06:59:42]

Description was changed from

==========
Revert of Remove PaintInfo's paintingRoot (patchset #5 id:80001 of
https://codereview.chromium.org/1602513004/ )

Reason for revert:
Broke oilpan and closed the tree:
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Oilpan...

I'll fix this tomorrow and reland.

Original issue's description:
> Remove PaintInfo's paintingRoot
> 
> PaintInfo had a paintingRoot member for supporting drawing a single
> layout object (including descendants). This complexity is spread
> throughout the painting code and only exists to support drag and drop
> drag images:
>
https://chromium.googlesource.com/chromium/src/+/65e7e9d4860e50bb677228f0b838...
> 
> This patch switches to directly painting LayoutObjects and removes the
> complex paintingRoot code.
> 
> ClusterTelemetry results: 0.5% record time savings:
>
https://storage.cloud.google.com/cluster-telemetry/tasks/chromium_perf_runs/p...
> 
> BUG=577004
> 
> Committed: https://crrev.com/63c9596d206c896b35ae8a5bff4db73847f62f33
> Cr-Commit-Position: refs/heads/master@{#370334}

TBR=chrishtr@chromium.org,wangxianzhu@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=577004
==========

to

==========
Revert of Remove PaintInfo's paintingRoot (patchset #5 id:80001 of
https://codereview.chromium.org/1602513004/ )

Reason for revert:
Broke oilpan and closed the tree:
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Oilpan...

I'll fix this tomorrow and reland.

Original issue's description:
> Remove PaintInfo's paintingRoot
>
> PaintInfo had a paintingRoot member for supporting drawing a single
> layout object (including descendants). This complexity is spread
> throughout the painting code and only exists to support drag and drop
> drag images:
>
https://chromium.googlesource.com/chromium/src/+/65e7e9d4860e50bb677228f0b838...
>
> This patch switches to directly painting LayoutObjects and removes the
> complex paintingRoot code.
>
> ClusterTelemetry results: 0.5% record time savings:
>
https://storage.cloud.google.com/cluster-telemetry/tasks/chromium_perf_runs/p...
>
> BUG=577004
>
> Committed: https://crrev.com/63c9596d206c896b35ae8a5bff4db73847f62f33
> Cr-Commit-Position: refs/heads/master@{#370334}

TBR=chrishtr@chromium.org,wangxianzhu@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=577004

Committed: https://crrev.com/ce37a6c4442ded2ffd29703b27d77e126528f3f4
Cr-Commit-Position: refs/heads/master@{#370335}
==========

[commit-bot: I haz the power, 2016-01-20 06:59:43]

Patchset 1 (id:??) landed as
https://crrev.com/ce37a6c4442ded2ffd29703b27d77e126528f3f4
Cr-Commit-Position: refs/heads/master@{#370335}