Reland: Refactor unreliable hit test code to avoid owning_layers

Reland: Refactor unreliable hit test code to avoid owning_layers

In [1] we switched the unreliable hit test code from using ScrollNode's
owning_layer to using the ScrollTree's layer_id_to_scroll_node_index.
This patch improves on [1] to not use layer_id_to_scroll_node_index
either, which turned out to be owning_layer in disguise.

The existing IsClosestScrollAncestor code has been refactored into a
helper (IsInitialScrollHitTestReliable) that makes the main thread
fallback cases more obvious (see: [2,3]). A test has been added for
the failure case noticed by Ali Juma in [1] where a drawn scrollbar
is the child of a scrolling layer but itself does not scroll.

[1] https://codereview.chromium.org/2702143002
[2] https://codereview.chromium.org/238803005
[3] https://codereview.chromium.org/1878323002

This is a reland of https://codereview.chromium.org/2718833002 which
was rolled out but turned out to not be the actual cause of
https://crbug.com/696919.

TBR=ajuma@chromium.org
BUG=693740
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2720713004
Cr-Commit-Position: refs/heads/master@{#453686}
Committed: https://chromium.googlesource.com/chromium/src/+/dbe75656dc50037306c8a3b6968a5592f4b17106

[pdr., 2017-02-28 19:13:59]

Description was changed from

==========
Reland: Refactor unreliable hit test code to avoid owning_layers

In [1] we switched the unreliable hit test code from using ScrollNode's
owning_layer to using the ScrollTree's layer_id_to_scroll_node_index.
This patch improves on [1] to not use layer_id_to_scroll_node_index
either, which turned out to be owning_layer in disguise.

The existing IsClosestScrollAncestor code has been refactored into a
helper (IsInitialScrollHitTestReliable) that makes the main thread
fallback cases more obvious (see: [2,3]). A test has been added for
the failure case noticed by Ali Juma in [1] where a drawn scrollbar
is the child of a scrolling layer but itself does not scroll.

[1] https://codereview.chromium.org/2702143002
[2] https://codereview.chromium.org/238803005
[3] https://codereview.chromium.org/1878323002

This is a reland of https://codereview.chromium.org/2718833002 which
was rolled out but turned out to not be the actual cause of
https://crbug.com/696919.

TBR=ajuma@chromium.org
BUG=693740
==========

to

==========
Reland: Refactor unreliable hit test code to avoid owning_layers

In [1] we switched the unreliable hit test code from using ScrollNode's
owning_layer to using the ScrollTree's layer_id_to_scroll_node_index.
This patch improves on [1] to not use layer_id_to_scroll_node_index
either, which turned out to be owning_layer in disguise.

The existing IsClosestScrollAncestor code has been refactored into a
helper (IsInitialScrollHitTestReliable) that makes the main thread
fallback cases more obvious (see: [2,3]). A test has been added for
the failure case noticed by Ali Juma in [1] where a drawn scrollbar
is the child of a scrolling layer but itself does not scroll.

[1] https://codereview.chromium.org/2702143002
[2] https://codereview.chromium.org/238803005
[3] https://codereview.chromium.org/1878323002

This is a reland of https://codereview.chromium.org/2718833002 which
was rolled out but turned out to not be the actual cause of
https://crbug.com/696919.

TBR=ajuma@chromium.org
BUG=693740
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
==========

[pdr., 2017-02-28 19:14:40]

The CQ bit was checked by pdr@chromium.org

[commit-bot: I haz the power, 2017-02-28 19:15:10]

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, 2017-02-28 20:23:09]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1488309280541020, "parent_rev":
"f9671b26418b5a1c11cd23f56e747a3941b78aaa", "commit_rev":
"dbe75656dc50037306c8a3b6968a5592f4b17106"}

[commit-bot: I haz the power, 2017-02-28 20:23:50]

Description was changed from

==========
Reland: Refactor unreliable hit test code to avoid owning_layers

In [1] we switched the unreliable hit test code from using ScrollNode's
owning_layer to using the ScrollTree's layer_id_to_scroll_node_index.
This patch improves on [1] to not use layer_id_to_scroll_node_index
either, which turned out to be owning_layer in disguise.

The existing IsClosestScrollAncestor code has been refactored into a
helper (IsInitialScrollHitTestReliable) that makes the main thread
fallback cases more obvious (see: [2,3]). A test has been added for
the failure case noticed by Ali Juma in [1] where a drawn scrollbar
is the child of a scrolling layer but itself does not scroll.

[1] https://codereview.chromium.org/2702143002
[2] https://codereview.chromium.org/238803005
[3] https://codereview.chromium.org/1878323002

This is a reland of https://codereview.chromium.org/2718833002 which
was rolled out but turned out to not be the actual cause of
https://crbug.com/696919.

TBR=ajuma@chromium.org
BUG=693740
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
==========

to

==========
Reland: Refactor unreliable hit test code to avoid owning_layers

In [1] we switched the unreliable hit test code from using ScrollNode's
owning_layer to using the ScrollTree's layer_id_to_scroll_node_index.
This patch improves on [1] to not use layer_id_to_scroll_node_index
either, which turned out to be owning_layer in disguise.

The existing IsClosestScrollAncestor code has been refactored into a
helper (IsInitialScrollHitTestReliable) that makes the main thread
fallback cases more obvious (see: [2,3]). A test has been added for
the failure case noticed by Ali Juma in [1] where a drawn scrollbar
is the child of a scrolling layer but itself does not scroll.

[1] https://codereview.chromium.org/2702143002
[2] https://codereview.chromium.org/238803005
[3] https://codereview.chromium.org/1878323002

This is a reland of https://codereview.chromium.org/2718833002 which
was rolled out but turned out to not be the actual cause of
https://crbug.com/696919.

TBR=ajuma@chromium.org
BUG=693740
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2720713004
Cr-Commit-Position: refs/heads/master@{#453686}
Committed:
https://chromium.googlesource.com/chromium/src/+/dbe75656dc50037306c8a3b6968a...
==========

[commit-bot: I haz the power, 2017-02-28 20:23:51]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/dbe75656dc50037306c8a3b6968a...