Make having an existing ancestor overflow layer when adding a PaintLayer fatal.

Make having an existing ancestor overflow layer when adding a PaintLayer fatal.

When a PaintLayer is added it should not have an existing ancestor overflow
layer as it could be at best incorrect, and at worst point to a PaintLayer which
has / will be deleted without notifying the layer. This check used to be debug
only but we are seeing a crash likely due to an invalid ancestor overflow layer
so adding this check should help find the code path where it is added.

BUG=679170
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2631193002
Cr-Commit-Position: refs/heads/master@{#444207}
Committed: https://chromium.googlesource.com/chromium/src/+/36f7d1fc579ca461cb46cefb3f5598139056c681

[flackr, 2017-01-16 16:29:29]

Description was changed from

==========
Make having an existing ancestor overflow layer when adding a PaintLayer fatal.

When a PaintLayer is added it should not have an existing ancestor overflow
layer as it could be at best incorrect, and at worst point to a PaintLayer which
has / will be deleted without notifying the layer. This check used to be debug
only but we are seeing a crash likely due to an invalid ancestor overflow layer
so adding this check should help find the code path where it is added.

BUG=679170
==========

to

==========
Make having an existing ancestor overflow layer when adding a PaintLayer fatal.

When a PaintLayer is added it should not have an existing ancestor overflow
layer as it could be at best incorrect, and at worst point to a PaintLayer which
has / will be deleted without notifying the layer. This check used to be debug
only but we are seeing a crash likely due to an invalid ancestor overflow layer
so adding this check should help find the code path where it is added.

BUG=679170
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

[flackr, 2017-01-16 16:34:08]

flackr@chromium.org changed reviewers:
+ chrishtr@chromium.org

[flackr, 2017-01-16 16:34:08]

I haven't been able to figure out how we could get a PaintLayer with an obsolete
/ invalid ancestor overflow layer, but if there is a code path where one is
added it should hit the CHECK in this patch which should point to the codepath
that adds it, WDYT?

[flackr, 2017-01-17 22:08:58]

ping?

[chrishtr, 2017-01-17 22:44:03]

lgtm

[flackr, 2017-01-17 22:45:57]

The CQ bit was checked by flackr@chromium.org

[commit-bot: I haz the power, 2017-01-17 22:46:43]

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, 2017-01-18 00:39:37]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1484693157762880, "parent_rev":
"0be65cf99ef32ab76ec17d496ceaed605e89ddcf", "commit_rev":
"36f7d1fc579ca461cb46cefb3f5598139056c681"}

[commit-bot: I haz the power, 2017-01-18 00:40:13]

Description was changed from

==========
Make having an existing ancestor overflow layer when adding a PaintLayer fatal.

When a PaintLayer is added it should not have an existing ancestor overflow
layer as it could be at best incorrect, and at worst point to a PaintLayer which
has / will be deleted without notifying the layer. This check used to be debug
only but we are seeing a crash likely due to an invalid ancestor overflow layer
so adding this check should help find the code path where it is added.

BUG=679170
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
==========

to

==========
Make having an existing ancestor overflow layer when adding a PaintLayer fatal.

When a PaintLayer is added it should not have an existing ancestor overflow
layer as it could be at best incorrect, and at worst point to a PaintLayer which
has / will be deleted without notifying the layer. This check used to be debug
only but we are seeing a crash likely due to an invalid ancestor overflow layer
so adding this check should help find the code path where it is added.

BUG=679170
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2631193002
Cr-Commit-Position: refs/heads/master@{#444207}
Committed:
https://chromium.googlesource.com/chromium/src/+/36f7d1fc579ca461cb46cefb3f55...
==========

[commit-bot: I haz the power, 2017-01-18 00:40:14]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/36f7d1fc579ca461cb46cefb3f55...