Here is an accessibility bug that you might be interested to look into. Feel free to assign it back to me if you don't want to take this on.
1. Open "content/browser/accessibility/dump_accessibility_events_browsertest.cc", find the test "AccessibilityEventsMenuListNext" and enable it to run on the Mac.
2. Run the test usint:
ninja -C out/Debug content_browsertestsout/Debug/content_browsertests --gtest_filter=*AccessibilityEventsMenuListNext*
3. Observe that it crashes with the following stack trace.

BrowserTestBase signal handler received SIGTERM. Backtrace:
0   libbase.dylib                       0x000000010246ef4f _ZN4base5debug10StackTraceC2Ev + 47
1   libbase.dylib                       0x000000010246f013 _ZN4base5debug10StackTraceC1Ev + 35
2   content_browsertests                0x0000000100b06b4a _ZN7content12_GLOBAL__N_1L27DumpStackTraceSignalHandlerEi + 74
3   libsystem_platform.dylib            0x00007fff92b2f5aa _sigtramp + 26
4   ???                                 0x00007fe74a812e80 0x0 + 140631364152960
5   CoreFoundation                      0x00007fff96faaf15 __CFRunLoopServiceMachPort + 181
6   CoreFoundation                      0x00007fff96faa539 __CFRunLoopRun + 1161
7   CoreFoundation                      0x00007fff96fa9e75 CFRunLoopRunSpecific + 309
8   HIToolbox                           0x00007fff95439a0d RunCurrentEventLoopInMode + 226
9   HIToolbox                           0x00007fff954397b7 ReceiveNextEventCommon + 479
10  HIToolbox                           0x00007fff954875cd AcquireNextEventInMode + 51
11  HIToolbox                           0x00007fff9548505a _ZL19IsUserStillTrackingP14MenuSelectDataPh + 186
12  HIToolbox                           0x00007fff95484c61 _ZL15TrackMenuCommonR14MenuSelectDataPh + 1545
13  HIToolbox                           0x00007fff9546d0d6 _ZL19PopUpMenuSelectCoreP8MenuData5PointdS1_tjPK4RecttjS4_S4_PK10__CFStringPP13OpaqueMenuRefPt + 1526
14  HIToolbox                           0x00007fff9546c2f6 _HandlePopUpMenuSelection7 + 596
15  AppKit                              0x00007fff8f90b161 _NSSLMPopUpCarbonMenu3 + 4153
16  AppKit                              0x00007fff8f90a116 _NSPopUpCarbonMenu3 + 39
17  AppKit                              0x00007fff8f909dd6 -[NSCarbonMenuImpl popUpMenu:atLocation:width:forView:withSelectedItem:withFont:withFlags:withOptions:] + 350
18  AppKit                              0x00007fff8f908a87 -[NSPopUpButtonCell trackMouse:inRect:ofView:untilMouseUp:] + 531
19  libcontent.dylib                    0x00000001065c2580 -[WebMenuRunner runMenuInView:withBounds:initialIndex:] + 1152
20  libcontent.dylib                    0x0000000105cf5ebb _ZN7content15PopupMenuHelper13ShowPopupMenuERKN3gfx4RectEidiRKNSt3__16vectorINS_8MenuItemENS5_9allocatorIS7_EEEEbb + 971
21  libcontent.dylib                    0x00000001069f0de7 _ZN7content18WebContentsViewMac13ShowPopupMenuEPNS_15RenderFrameHostERKN3gfx4RectEidiRKNSt3__16vectorINS_8MenuItemENS7_9allocatorIS9_EEEEbb + 535
22  libcontent.dylib                    0x00000001069f0f72 _ZThn8_N7content18WebContentsViewMac13ShowPopupMenuEPNS_15RenderFrameHostERKN3gfx4RectEidiRKNSt3__16vectorINS_8MenuItemENS7_9allocatorIS9_EEEEbb + 146
23  libcontent.dylib                    0x0000000105d0fc52 _ZN7content19RenderFrameHostImpl11OnShowPopupERK29FrameHostMsg_ShowPopup_Params + 322
24  libcontent.dylib                    0x0000000105d2e6df _ZN4base20DispatchToMethodImplIPN7content19RenderFrameHostImplEMS2_FvRK29FrameHostMsg_ShowPopup_ParamsEJS4_EJLm0EEEEvRKT_T0_RKNSt3__15tupleIJDpT1_EEENS_13IndexSequenceIJXspT2_EEEE + 175
25  libcontent.dylib                    0x0000000105d2e603 _ZN4base16DispatchToMethodIPN7content19RenderFrameHostImplEMS2_FvRK29FrameHostMsg_ShowPopup_ParamsEJS4_EEEvRKT_T0_RKNSt3__15tupleIJDpT1_EEE + 83
26  libcontent.dylib                    0x0000000105d2e58d _ZN3IPC16DispatchToMethodIN7content19RenderFrameHostImplEMS2_FvRK29FrameHostMsg_ShowPopup_ParamsEvNSt3__15tupleIJS3_EEEEEvPT_T0_PT1_RKT2_ + 93
27  libcontent.dylib                    0x0000000105d0fa95 _ZN3IPC8MessageTI27FrameHostMsg_ShowPopup_MetaNSt3__15tupleIJ29FrameHostMsg_ShowPopup_ParamsEEEvE8DispatchIN7content19RenderFrameHostImplES9_vMS9_FvRKS4_EEEbPKNS_7MessageEPT_PT0_PT1_T2_ + 517
28  libcontent.dylib                    0x0000000105d018e1 _ZN7content19RenderFrameHostImpl17OnMessageReceivedERKN3IPC7MessageE + 9905
29  libcontent.dylib                    0x00000001064eecc3 _ZN7content21RenderProcessHostImpl17OnMessageReceivedERKN3IPC7MessageE + 2179
30  libcontent.dylib                    0x00000001064f06c2 _ZThn8_N7content21RenderProcessHostImpl17OnMessageReceivedERKN3IPC7MessageE + 50