Reland "Box shadow should be recorded as main thread scrolling reasons for non-root layers."

Reland "Box shadow should be recorded as main thread scrolling reasons for non-root layers." (patchset #2 id:20001 of https://codereview.chromium.org/2676333002/ )

Reason for revert:
Reverted patch wasn't responsible for regression.

Original issue's description:
> Bisect job found this CL several times suspecting that it caused regression on nexus5p(crbug.com/685182). Revert it for now.
> 
> This reverts commit c83ddee4e5dcb0fdce873021c2701c9c3a2c547a.
> 
> BUG=
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
> 
> Review-Url: https://codereview.chromium.org/2676333002
> Cr-Commit-Position: refs/heads/master@{#448326}
> Committed: https://chromium.googlesource.com/chromium/src/+/95d4abb16bc2444b187772d3a4ee461503d4b7a7

TBR=ajuma@chromium.org,jwd@chromium.org,yigu@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=

[bokan, 2017-02-07 20:51:31]

The CQ bit was checked by bokan@chromium.org

[bokan, 2017-02-07 20:51:31]

Created Revert of Revert "Box shadow should be recorded as main thread scrolling
reasons for non-root layers."

[bokan, 2017-02-07 20:52:14]

Description was changed from

==========
Revert of Revert "Box shadow should be recorded as main thread scrolling reasons
for non-root layers." (patchset #2 id:20001 of
https://codereview.chromium.org/2676333002/ )

Reason for revert:
Reverted patch wasn't responsible for regression.

Original issue's description:
> Bisect job found this CL several times suspecting that it caused regression on
nexus5p(crbug.com/685182). Revert it for now.
> 
> This reverts commit c83ddee4e5dcb0fdce873021c2701c9c3a2c547a.
> 
> BUG=
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
> 
> Review-Url: https://codereview.chromium.org/2676333002
> Cr-Commit-Position: refs/heads/master@{#448326}
> Committed:
https://chromium.googlesource.com/chromium/src/+/95d4abb16bc2444b187772d3a4ee...

TBR=ajuma@chromium.org,jwd@chromium.org,yigu@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=
==========

to

==========
Reland "Box shadow should be recorded as main thread scrolling reasons for
non-root layers." (patchset #2 id:20001 of
https://codereview.chromium.org/2676333002/ )

Reason for revert:
Reverted patch wasn't responsible for regression.

Original issue's description:
> Bisect job found this CL several times suspecting that it caused regression on
nexus5p(crbug.com/685182). Revert it for now.
> 
> This reverts commit c83ddee4e5dcb0fdce873021c2701c9c3a2c547a.
> 
> BUG=
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
> 
> Review-Url: https://codereview.chromium.org/2676333002
> Cr-Commit-Position: refs/heads/master@{#448326}
> Committed:
https://chromium.googlesource.com/chromium/src/+/95d4abb16bc2444b187772d3a4ee...

TBR=ajuma@chromium.org,jwd@chromium.org,yigu@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=
==========

[commit-bot: I haz the power, 2017-02-07 20:52:31]

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