CL: https://chromium-review.googlesource.com/c/chromium/src/+/1382670/3

Failing build: https://ci.chromium.org/p/chromium/builders/luci.chromium.try/mac_chromium_rel_ng/212638

Build succeeds on retry:
https://ci.chromium.org/p/chromium/builders/luci.chromium.try/mac_chromium_rel_ng/212654

Failing task: https://chromium-swarm.appspot.com/task?id=41e391142db38810&refresh=10&show_raw=1
There appears to have been several reference image mismatches, and later there was a crash.

"""
9238:775:1220/003743.727815:INFO:CONSOLE(14)] "undefined", source: http://127.0.0.1:51970/content/test/data/gpu/pixel_webgl_sad_canvas.html (14)
Received signal 11 SEGV_MAPERR 000000000000
DevTools console [network]: Failed to load resource: the server responded with a status of 404 (File not found) http://127.0.0.1:51970/favicon.ico
0   Chromium Framework                  0x00000001233c7f5f base::debug::StackTrace::StackTrace(unsigned long) + 31
1   Chromium Framework                  0x00000001233c7db1 base::debug::(anonymous namespace)::StackDumpSignalHandler(int, __siginfo*, void*) + 2385
2   libsystem_platform.dylib            0x00007fff4fd70f5a _sigtramp + 26
3   ???                                 0x00007fbbf0809208 0x0 + 140445170569736
4   Chromium Framework                  0x000000012545853c gpu::GpuChannel::OnControlMessageReceived(IPC::Message const&) + 236
5   Chromium Framework                  0x000000012545986c gpu::GpuChannel::HandleMessageHelper(IPC::Message const&) + 140
6   Chromium Framework                  0x000000012545a970 base::internal::Invoker<base::internal::BindState<void (gpu::GpuChannel::*)(IPC::Message const&), base::WeakPtr<gpu::GpuChannel>, IPC::Message>, void ()>::RunOnce(base::internal::BindStateBase*) + 192
7   Chromium Framework                  0x00000001232adee1 base::debug::TaskAnnotator::RunTask(char const*, base::PendingTask*) + 305
8   Chromium Framework                  0x000000012335d0fa base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::DoWorkImpl(base::TimeTicks*) + 650
9   Chromium Framework                  0x00000001232e1bf3 base::MessagePumpCFRunLoopBase::RunWork() + 51
10  Chromium Framework                  0x00000001232c76da base::mac::CallWithEHFrame(void () block_pointer) + 10
11  Chromium Framework                  0x00000001232e13cf base::MessagePumpCFRunLoopBase::RunWorkSource(void*) + 63
12  CoreFoundation                      0x00007fff27c43a11 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
13  CoreFoundation                      0x00007fff27cfd42c __CFRunLoopDoSource0 + 108
14  CoreFoundation                      0x00007fff27c26470 __CFRunLoopDoSources0 + 208
15  CoreFoundation                      0x00007fff27c258ed __CFRunLoopRun + 1293
16  CoreFoundation                      0x00007fff27c25153 CFRunLoopRunSpecific + 483
17  Foundation                          0x00007fff29d21f26 -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 277
18  Chromium Framework                  0x00000001232e2461 base::MessagePumpNSRunLoop::DoRun(base::MessagePump::Delegate*) + 113
19  Chromium Framework                  0x00000001232e0d3f base::MessagePumpCFRunLoopBase::Run(base::MessagePump::Delegate*) + 127
20  Chromium Framework                  0x000000012335d86b base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::Run(bool) + 155
21  Chromium Framework                  0x000000012331a1b9 base::RunLoop::Run() + 249
22  Chromium Framework                  0x00000001294f3374 content::GpuMain(content::MainFunctionParams const&) + 1412
23  Chromium Framework                  0x0000000122c90503 content::ContentMainRunnerImpl::Run(bool) + 435
24  Chromium Framework                  0x0000000126291a55 service_manager::Main(service_manager::MainParams const&) + 3173
25  Chromium Framework                  0x0000000122c8f614 content::ContentMain(content::ContentMainParams const&) + 68
26  Chromium Framework                  0x000000011ec2715f ChromeMain + 175
27  Chromium Helper                     0x000000010efd272e main + 494
28  libdyld.dylib                       0x00007fff4fa62015 start + 1
[end of stack trace]
[9238:775:1220/003743.930106:INFO:CONSOLE(0)] "WebGL: CONTEXT_LOST_WEBGL: loseContext: context lost", source: http://127.0.0.1:51970/content/test/data/gpu/pixel_webgl_sad_canvas.html (0)
"""

This test was run on 12/20 3:30AM EST, which was after this revert landed [from a previous problem]:
https://chromium-review.googlesource.com/c/chromium/src/+/1283010