Automatically applying components based on crash stacktrace and information from OWNERS files.

If this is incorrect, please apply the Test-Predator-Wrong-Components label.

Automatically assigning owner based on suspected regression changelist https://chromium.googlesource.com/chromium/src/+/f9daa687e026e5dfbc15c5558b13a378254f26bc (Avoid constructing scrollbars just to measure their thickness.).

If this is incorrect, please let us know why and apply the Test-Predator-Wrong-CLs label. If you aren't the correct owner for this issue, please unassign yourself as soon as possible so it can be re-triaged.

This is a serious security regression. If you are not able to fix this quickly, please revert the change that introduced it.

If this doesn't affect a release branch, or has not been properly classified for severity, please update the Security_Impact or Security_Severity labels, and remove the ReleaseBlock label. To disable this altogether, apply ReleaseBlock-NA.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9bf1dd559e10614f744e30042574954723346bf0

commit 9bf1dd559e10614f744e30042574954723346bf0
Author: Stefan Zager <szager@chromium.org>
Date: Sat Jul 07 01:21:21 2018

Custom scrollbars: differentiate between style source and containing box

The existing code conflates two concepts: the node that supplies the
custom scrollbar style, and the box that owns the ScrollableArea.
This patch splits the two concepts, and allows the style source node to
be inline. This only comes into play when styling the top-level
scrollbars, where the enclosing box is the LayoutView, but the style
source node may be the body or the document element.

BUG= 855896 
R=skobes@chromium.org

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ib911719766cf377b73baf367c523c37e01ee80b3
Reviewed-on: https://chromium-review.googlesource.com/1115972
Reviewed-by: Philip Rogers <pdr@chromium.org>
Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573136}
[add] https://crrev.com/9bf1dd559e10614f744e30042574954723346bf0/third_party/WebKit/LayoutTests/fast/scrolling/custom-scrollbar-inline-style-source.html
[modify] https://crrev.com/9bf1dd559e10614f744e30042574954723346bf0/third_party/blink/renderer/core/layout/layout_object.cc
[modify] https://crrev.com/9bf1dd559e10614f744e30042574954723346bf0/third_party/blink/renderer/core/layout/layout_scrollbar.cc
[modify] https://crrev.com/9bf1dd559e10614f744e30042574954723346bf0/third_party/blink/renderer/core/layout/layout_scrollbar.h
[modify] https://crrev.com/9bf1dd559e10614f744e30042574954723346bf0/third_party/blink/renderer/core/layout/layout_scrollbar_part.cc
[modify] https://crrev.com/9bf1dd559e10614f744e30042574954723346bf0/third_party/blink/renderer/core/layout/layout_scrollbar_part.h
[modify] https://crrev.com/9bf1dd559e10614f744e30042574954723346bf0/third_party/blink/renderer/core/paint/paint_layer_scrollable_area.cc

ClusterFuzz has detected this issue as fixed in range 573135:573136.

Detailed report: https://clusterfuzz.com/testcase?key=6230800882991104

Fuzzer: inferno_twister
Job Type: linux_asan_chrome_v8_arm
Platform Id: linux

Crash Type: Security DCHECK failure
Crash Address: 
Crash State:
  !object || (object->IsBox()) in layout_box.h
  blink::LayoutScrollbar::StyleSource
  blink::LayoutScrollbar::UpdateScrollbarPart
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=linux_asan_chrome_v8_arm&range=569704:569705
Fixed: https://clusterfuzz.com/revisions?job=linux_asan_chrome_v8_arm&range=573135:573136

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6230800882991104

See https://github.com/google/clusterfuzz-tools for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

This bug has been closed for more than 14 weeks. Removing security view restrictions.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot