Snippet of failure:

[ RUN      ] SplitViewControllerTest.AdjustTransientChildBounds
  =================================================================
  ==9304==ERROR: AddressSanitizer: heap-use-after-free on address 0x61400008ed60 at pc 0x0000094d0bea bp 0x7fff7d15bbf0 sp 0x7fff7d15bbe8
  READ of size 8 at 0x61400008ed60 thread T0
      #0 0x94d0be9 in begin buildtools/third_party/libc++/trunk/include/vector:1479:30
      #1 0x94d0be9 in HasObserver base/observer_list.h:302
      #2 0x94d0be9 in aura::Window::HasObserver(aura::WindowObserver const*) const ui/aura/window.cc:550
      #3 0x94ee113 in aura::WindowObserver::OnUnobservingWindow(aura::Window*) ui/aura/window_observer.cc:25:15
      #4 0x94c7667 in aura::Window::RemoveObserver(aura::WindowObserver*) ui/aura/window.cc:545:13
      #5 0x76fc645 in RemoveAll base/scoped_observer.h:45:20
      #6 0x76fc645 in ~ScopedObserver base/scoped_observer.h:26
      #7 0x76fc645 in ash::SplitViewDivider::~SplitViewDivider() ash/wm/splitview/split_view_divider.cc:310
      #8 0x76fc90d in ash::SplitViewDivider::~SplitViewDivider() ash/wm/splitview/split_view_divider.cc:303:39
      #9 0x76e641f in operator() buildtools/third_party/libc++/trunk/include/memory:2321:5
      #10 0x76e641f in reset buildtools/third_party/libc++/trunk/include/memory:2634
      #11 0x76e641f in ash::SplitViewController::EndSplitView(ash::SplitViewController::EndReason) ash/wm/splitview/split_view_controller.cc:576
      #12 0x76ef5fa in ash::SplitViewController::OnSnappedWindowDetached(aura::Window*) ash/wm/splitview/split_view_controller.cc:1146:5
      #13 0x76f1a43 in ash::SplitViewController::OnWindowDestroyed(aura::Window*) ash/wm/splitview/split_view_controller.cc:637:3
      #14 0x94c6354 in aura::Window::~Window() ui/aura/window.cc:142:14
      #15 0x94c7b8d in aura::Window::~Window() ui/aura/window.cc:94:19
      #16 0x9a5769f in views::NativeWidgetAura::~NativeWidgetAura() ui/views/widget/native_widget_aura.cc
      #17 0x9a5793d in views::NativeWidgetAura::~NativeWidgetAura() ui/views/widget/native_widget_aura.cc:1034:39
      #18 0x99ff867 in views::Widget::~Widget() ui/views/widget/widget.cc:189:5
      #19 0x9a005ed in views::Widget::~Widget() ui/views/widget/widget.cc:186:19
      #20 0x1bb90b4 in operator() buildtools/third_party/libc++/trunk/include/memory:2321:5
      #21 0x1bb90b4 in reset buildtools/third_party/libc++/trunk/include/memory:2634
      #22 0x1bb90b4 in ~unique_ptr buildtools/third_party/libc++/trunk/include/memory:2588
      #23 0x1bb90b4 in ash::SplitViewControllerTest_AdjustTransientChildBounds_Test::TestBody() ash/wm/splitview/split_view_controller_unittest.cc:1655
      #24 0x4db8612 in HandleExceptionsInMethodIfSupported<testing::Test, void> third_party/googletest/src/googletest/src/gtest.cc
      #25 0x4db8612 in testing::Test::Run() third_party/googletest/src/googletest/src/gtest.cc:2522
      #26 0x4dba544 in testing::TestInfo::Run() third_party/googletest/src/googletest/src/gtest.cc:2698:11
      #27 0x4dbb916 in testing::TestCase::Run() third_party/googletest/src/googletest/src/gtest.cc:2816:28
      #28 0x4de3366 in testing::internal::UnitTestImpl::RunAllTests() third_party/googletest/src/googletest/src/gtest.cc:5182:43
      #29 0x4de25b5 in HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool> third_party/googletest/src/googletest/src/gtest.cc
      #30 0x4de25b5 in testing::UnitTest::Run() third_party/googletest/src/googletest/src/gtest.cc:4791
      #31 0x7c55f8a in RUN_ALL_TESTS third_party/googletest/src/googletest/include/gtest/gtest.h:2333:46
      #32 0x7c55f8a in base::TestSuite::Run() base/test/test_suite.cc:295
      #33 0x7c5c677 in Run base/callback.h:99:12
      #34 0x7c5c677 in base::(anonymous namespace)::LaunchUnitTestsInternal(base::OnceCallback<int ()>, unsigned long, int, bool, base::OnceCallback<void ()>) base/test/launcher/unit_test_launcher.cc:225
      #35 0x7c5c120 in base::LaunchUnitTests(int, char**, base::OnceCallback<int ()>) base/test/launcher/unit_test_launcher.cc:576:10
      #36 0x182f467 in main ash/test/ash_unittests.cc:37:10
      #37 0x7f55099bdf44 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21f44)

Will try reverting crrev.com/c/1274197 to fix.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e41458e037d2d6eea8297dfee4006848bb6f123a

commit e41458e037d2d6eea8297dfee4006848bb6f123a
Author: Patti <patricialor@chromium.org>
Date: Fri Oct 12 02:14:27 2018

Revert "splitscreen: Adjust bubble dialog bounds if splitscreen is active."

This reverts commit c3acb7ba6a2b6565656736f3050bfc593baf4781.

Reason for revert: This change may be causing ash_unittests to fail on multiple builders - see  crbug.com/894683 

Original change's description:
> splitscreen: Adjust bubble dialog bounds if splitscreen is active.
> 
> When a dialog is added to a window that's currently showig in
> splitscreen, we should adjust the dialog bounds to show the dialog
> aligned within its own side of the split, rather than across the divider
> bar.
> 
> Note the divider is still placed on top of the snapped windows and its
> transient children if they are placed in default container.
> 
> Bug:  878268 
> Change-Id: Ibdd71f1d42aac419ef73ae9f7a2f78af6bf36880
> Reviewed-on: https://chromium-review.googlesource.com/c/1274197
> Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
> Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#598827}

TBR=xiyuan@chromium.org,xdai@chromium.org

Change-Id: I74d78ce0184d2028811872ac633da33ede16f296
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  878268 ,  894683 
Reviewed-on: https://chromium-review.googlesource.com/c/1277907
Reviewed-by: Patti <patricialor@chromium.org>
Commit-Queue: Patti <patricialor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599069}
[modify] https://crrev.com/e41458e037d2d6eea8297dfee4006848bb6f123a/ash/wm/splitview/split_view_controller_unittest.cc
[modify] https://crrev.com/e41458e037d2d6eea8297dfee4006848bb6f123a/ash/wm/splitview/split_view_divider.cc
[modify] https://crrev.com/e41458e037d2d6eea8297dfee4006848bb6f123a/ash/wm/splitview/split_view_divider.h

The failure hasn't occurred in days. Removing from sheriff queue.

It looks like r599069 fixed the problem, therefore assigning to the author of the reverted CL.

Yes, it should have been fixed.