See also https://chromium-swarm.appspot.com/task?id=41dbb1589e73c410&refresh=10&show_raw=1:

For instance MaterialBookmarksPolicyTest.All. There are many errors reported and I'm not sure which one caused the test to fail. My guess is on the failed assert.

[ RUN      ] MaterialBookmarksPolicyTest.All
[1:1:1218/120743.685204:INFO:hugepage_text.cc(68)] Mlocking text pages failed: Cannot allocate memory (12)
[6456:6456:1218/120744.818276:WARNING:chrome_browser_main_chromeos.cc(544)] Running as stub user with profile dir: test-user
[6456:6456:1218/120745.496416:WARNING:easy_unlock_service_regular.cc(441)] EasyUnlockServiceRegular::IsInLegacyHostMode: DeviceSyncClient not ready. Returning false.
[6456:6456:1218/120745.626689:INFO:remote_commands_service.cc(38)] Fetching remote commands.
[6456:6456:1218/120745.626832:WARNING:remote_commands_service.cc(40)] Client is not registered.
[6456:6456:1218/120745.626949:INFO:remote_commands_invalidator.cc(32)] Initialize RemoteCommandsInvalidator.
[6456:6456:1218/120745.627020:INFO:remote_commands_invalidator.cc(57)] Starting RemoteCommandsInvalidator.
[6456:6456:1218/120745.627090:INFO:remote_commands_invalidator.cc(123)] RemoteCommandsInvalidator ReloadPolicyData.
[6456:6456:1218/120745.627146:INFO:remote_commands_invalidator.cc(167)] Unregister RemoteCommandsInvalidator.
[6456:6456:1218/120745.807205:WARNING:wallpaper_controller_client.cc(358)] Cannot get wallpaper files id in RemovePolicyWallpaper. This should never happen under normal circumstances.
[6456:6456:1218/120746.298997:WARNING:personal_data_manager.cc(492)] 0xc28d5587020 refresh is done, notifying PersonalDataChanged
[6456:6456:1218/120746.370597:WARNING:personal_data_manager.cc(492)] 0xc28d5f44420 refresh is done, notifying PersonalDataChanged
[6456:6456:1218/120746.778801:ERROR:gpu_interface_provider.cc(87)] Not implemented reached in virtual void content::GpuInterfaceProvider::RegisterOzoneGpuInterfaces(service_manager::BinderRegistry *)
[6456:6456:1218/120747.447479:ERROR:remote_text_input_client.cc(150)] Not implemented reached in virtual void RemoteTextInputClient::OnInputMethodChanged()
[6456:6456:1218/120747.447555:ERROR:remote_text_input_client.cc(107)] Not implemented reached in virtual ui::TextInputClient::FocusReason RemoteTextInputClient::GetFocusReason() const
[6456:6456:1218/120747.447589:ERROR:remote_text_input_client.cc(191)] Not implemented reached in virtual bool RemoteTextInputClient::ShouldDoLearning()
[6456:6456:1218/120747.447678:ERROR:remote_text_input_client.cc(101)] Not implemented reached in virtual bool RemoteTextInputClient::HasCompositionText() const
[6456:6456:1218/120747.447714:ERROR:remote_text_input_client.cc(113)] Not implemented reached in virtual bool RemoteTextInputClient::GetTextRange(gfx::Range *) const
[6456:6456:1218/120748.079726:ERROR:render_widget_host_view_aura.cc(1298)] Not implemented reached in virtual base::i18n::TextDirection content::RenderWidgetHostViewAura::GetTextDirection() const
[6456:6456:1218/120748.916725:WARNING:CONSOLE(0)] "HTML Imports is deprecated and will be removed in M73, around March 2019. Please use ES modules instead. See https://www.chromestatus.com/features/5144752345317376 for more details.", source:  (0)
[6456:6456:1218/120751.012848:WARNING:CONSOLE(442)] "document.registerElement is deprecated and will be removed in M73, around March 2019. Please use window.customElements.define instead. See https://www.chromestatus.com/features/4642138092470272 for more details.", source: chrome://resources/polymer/v1_0/polymer/polymer-micro-extracted.js (442)
[6456:6456:1218/120752.756852:WARNING:CONSOLE(2083)] "Element.createShadowRoot is deprecated and will be removed in M73, around March 2019. Please use Element.attachShadow instead. See https://www.chromestatus.com/features/4507242028072960 for more details.", source: chrome://resources/polymer/v1_0/polymer/polymer-mini-extracted.js (2083)
[6456:6456:1218/120753.390772:INFO:CONSOLE(1281)] "Running TestCase MaterialBookmarksPolicyTest.All", source: file:///b/s/w/ir/chrome/test/data/webui/test_api.js (1281)
[6456:6456:1218/120753.592528:WARNING:CONSOLE(34)] "Error: Assertion failed
    at assert (chrome://resources/js/util.js:27:17)
    at Function.CommandManager.getInstance (chrome://bookmarks/command_manager.js:823:12)
    at Context.<anonymous> (file:///b/s/w/ir/chrome/test/data/webui/md_bookmarks/policy_test.js:28:53)
    at callFn (file:///b/s/w/ir/third_party/mocha/mocha.js:4471:21)
    at Test.Runnable.run (file:///b/s/w/ir/third_party/mocha/mocha.js:4464:7)
    at Runner.runTest (file:///b/s/w/ir/third_party/mocha/mocha.js:4934:10)
    at file:///b/s/w/ir/third_party/mocha/mocha.js:5040:12
    at next (file:///b/s/w/ir/third_party/mocha/mocha.js:4854:14)
    at file:///b/s/w/ir/third_party/mocha/mocha.js:4864:7
    at next (file:///b/s/w/ir/third_party/mocha/mocha.js:4796:14)", source: chrome://resources/js/util.js (34)
[6456:6456:1218/120753.593719:ERROR:CONSOLE(48)] "Mocha test failed: Bookmarks policies incognito availability updates when changed
Error: Assertion failed
    at assert (chrome://resources/js/util.js:27:17)
    at Function.CommandManager.getInstance (command_manager.js:823:12)
    at Context.<anonymous> (file:///b/s/w/ir/chrome/test/data/webui/md_bookmarks/policy_test.js:28:53)
", source: file:///b/s/w/ir/chrome/test/data/webui/mocha_adapter.js (48)
[6456:6456:1218/120754.906039:WARNING:CONSOLE(385)] "
Accessibility issues found on chrome://bookmarks/
*** Begin accessibility audit results ***
An accessibility audit found 
Errors:
Error: AX_ARIA_09 (Elements with ARIA roles must be in the correct scope) failed on the following element:
#list > BOOKMARKS-ITEM
See https://github.com/GoogleChrome/accessibility-developer-tools/wiki/Audit-Rules#ax_aria_09 for more information.

Error: AX_ARIA_04 (ARIA state and property values must be valid) failed on the following elements (1 - 5 of 5):
#searchInput
#menuButton
#container
#container
#menuButton
See https://github.com/GoogleChrome/accessibility-developer-tools/wiki/Audit-Rules#ax_aria_04 for more information.

Error: AX_ARIA_02 (ARIA attributes which refer to other elements by ID should refer to elements which exist in the DOM) failed on the following elements (1 - 3 of 3):
#searchInput
#container
#container
See https://github.com/GoogleChrome/accessibility-developer-tools/wiki/Audit-Rules#ax_aria_02 for more information.


*** End accessibility audit results ***", source: file:///b/s/w/ir/chrome/test/data/webui/test_api.js (385)
[6456:6456:1218/120754.909919:ERROR:web_ui_test_handler.cc(100)] Test Errors: 1/2 tests had failed assertions.
[6456:6456:1218/120754.910180:ERROR:web_ui_browser_test.cc(488)] CONDITION FAILURE: encountered javascript console error(s):
[6456:6456:1218/120754.910221:ERROR:web_ui_browser_test.cc(490)] JS ERROR: '[6456:6456:1218/120753.593719:ERROR:CONSOLE(48)] "Mocha test failed: Bookmarks policies incognito availability updates when changed
Error: Assertion failed
    at assert (chrome://resources/js/util.js:27:17)
    at Function.CommandManager.getInstance (command_manager.js:823:12)
    at Context.<anonymous> (file:///b/s/w/ir/chrome/test/data/webui/md_bookmarks/policy_test.js:28:53)
", source: file:///b/s/w/ir/chrome/test/data/webui/mocha_adapter.js (48)
'
[6456:6456:1218/120754.910266:ERROR:web_ui_browser_test.cc(492)] JS call assumed failed, because JS console error(s) found.
gen/chrome/test/data/webui/md_bookmarks/md_bookmarks_browsertest-gen.cc:507: Failure
Value of: RunJavascriptTestF( true, "MaterialBookmarksPolicyTest", "All")
  Actual: false
Expected: true
Stack trace:
#0 0x555dba106550 StackTraceGetter::CurrentStackTrace()
#1 0x555dba127e67 testing::internal::UnitTestImpl::CurrentOsStackTraceExceptTop()
#2 0x555dba1272c3 testing::internal::AssertHelper::operator=()
#3 0x555db8db2070 MaterialBookmarksPolicyTest_All_Test::RunTestOnMainThread()
#4 0x555dbee2c785 content::BrowserTestBase::ProxyRunTestOnMainThreadLoop()
#5 0x555db628f83d _ZN4base8internal13FunctorTraitsIM25RenderViewContextMenuBaseFvvEvE6InvokeIS4_P21RenderViewContextMenuJEEEvT_OT0_DpOT1_
#6 0x555db628f784 _ZN4base8internal12InvokeHelperILb0EvE8MakeItSoIM25RenderViewContextMenuBaseFvvEJP21RenderViewContextMenuEEEvOT_DpOT0_
#7 0x555dbee2f5e5 _ZN4base8internal7InvokerINS0_9BindStateIMN7content15BrowserTestBaseEFvvEJNS0_17UnretainedWrapperIS4_EEEEEFvvEE7RunImplIRKS6_RKNSt3__15tupleIJS8_EEEJLm0EEEEvOT_OT0_NSF_16integer_sequenceImJXspT1_EEEE
#8 0x555dbee2f51c _ZN4base8internal7InvokerINS0_9BindStateIMN7content15BrowserTestBaseEFvvEJNS0_17UnretainedWrapperIS4_EEEEEFvvEE3RunEPNS0_13BindStateBaseE
#9 0x555db627ff6d _ZNKR4base17RepeatingCallbackIFvvEE3RunEv
#10 0x555dbdb576b0 ChromeBrowserMainParts::PreMainMessageLoopRunImpl()
#11 0x555dbdb55844 ChromeBrowserMainParts::PreMainMessageLoopRun()
#12 0x555db92207ab chromeos::ChromeBrowserMainPartsChromeos::PreMainMessageLoopRun()
#13 0x7f3f5777dc42 content::BrowserMainLoop::PreMainMessageLoopRun()
#14 0x7f3f56353f0d _ZN4base8internal13FunctorTraitsIMN7content12ChildProcessEFvvEvE6InvokeIS5_PS3_JEEEvT_OT0_DpOT1_
#15 0x7f3f56353e54 _ZN4base8internal12InvokeHelperILb0EvE8MakeItSoIMN7content12ChildProcessEFvvEJPS5_EEEvOT_DpOT0_
#16 0x7f3f577839c5 _ZN4base8internal7InvokerINS0_9BindStateIMN7content15BrowserMainLoopEFivEJNS0_17UnretainedWrapperIS4_EEEEEFivEE7RunImplIRKS6_RKNSt3__15tupleIJS8_EEEJLm0EEEEiOT_OT0_NSF_16integer_sequenceImJXspT1_EEEE
#17 0x7f3f577838fc _ZN4base8internal7InvokerINS0_9BindStateIMN7content15BrowserMainLoopEFivEJNS0_17UnretainedWrapperIS4_EEEEEFivEE3RunEPNS0_13BindStateBaseE
#18 0x7f3f56258b4d _ZNKR4base17RepeatingCallbackIFvvEE3RunEv
#19 0x7f3f58771e2d content::StartupTaskRunner::RunAllTasksNow()
#20 0x7f3f5777979f content::BrowserMainLoop::CreateStartupTasks()
#21 0x7f3f57786043 content::BrowserMainRunnerImpl::Initialize()
#22 0x7f3f577710b9 content::BrowserMain()
#23 0x7f3f59aed710 content::RunBrowserProcessMain()
#24 0x7f3f59af0b85 content::ContentMainRunnerImpl::RunServiceManager()
#25 0x7f3f59aef749 content::ContentMainRunnerImpl::Run()
#26 0x7f3f59ae650c content::ContentServiceManagerMainDelegate::RunEmbedderProcess()
#27 0x7f3f2c22b9d1 service_manager::Main()
#28 0x7f3f59aeae25 content::ContentMain()
#29 0x555dbee2bd32 content::BrowserTestBase::SetUp()
#30 0x555dbd9f6acb InProcessBrowserTest::SetUp()
#31 0x555db62e17fe _ZN7testing8internal12InvokeHelperIRKNSt3__16vectorIPN12user_manager4UserENS2_9allocatorIS6_EEEENS2_5tupleIJEEEE12InvokeMethodIN8chromeos15MockUserManagerEMSH_KFSB_vEEESB_PT_T0_RKSD_

[6682:6682:1218/120755.349919:ERROR:gles2_cmd_decoder.cc(18098)] [.BrowserCompositor-0xc28d767ac20]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[6682:6682:1218/120755.350169:ERROR:gles2_cmd_decoder.cc(10449)] [.BrowserCompositor-0xc28d767ac20]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[6682:6682:1218/120755.350335:ERROR:gles2_cmd_decoder.cc(18098)] [.BrowserCompositor-0xc28d767ac20]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[6682:6682:1218/120755.350489:ERROR:gles2_cmd_decoder.cc(10449)] [.BrowserCompositor-0xc28d767ac20]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[6456:6456:1218/120755.731062:ERROR:http_bridge.cc(126)] Not implemented reached in virtual void syncer::HttpBridgeFactory::OnSignalReceived()
[6456:6456:1218/120755.735336:INFO:remote_commands_invalidator.cc(45)] Shutdown RemoteCommandsInvalidator.
[6456:6456:1218/120755.735453:INFO:remote_commands_invalidator.cc(68)] Stopping RemoteCommandsInvalidator.
[6456:6456:1218/120755.735503:INFO:remote_commands_invalidator.cc(167)] Unregister RemoteCommandsInvalidator.
[6456:6659:1218/120755.855541:WARNING:discardable_shared_memory_manager.cc(410)] Some MojoDiscardableSharedMemoryManagerImpls are still alive. They will be leaked.
[6456:6892:1218/120755.863344:WARNING:internal_linux.cc(64)] Failed to read /proc/6682/stat
[6456:6456:1218/120755.879432:WARNING:pref_notifier_impl.cc(23)] Pref observer found at shutdown.
[6456:6456:1218/120755.879524:WARNING:pref_notifier_impl.cc(23)] Pref observer found at shutdown.
[  FAILED  ] MaterialBookmarksPolicyTest.All, where TypeParam =  and GetParam() =  (13659 ms)

Already reverted:
https://chromium-review.googlesource.com/c/chromium/src/+/1383113

Closing since the sheriff already reverted. FWIW, check the messages on the culprit CL to avoid trying to revert twice.