void MigrateTaskbarPins() {
  [...]
  base::PostTaskWithTraits(FROM_HERE,
                           {base::MayBlock(), base::TaskPriority::BACKGROUND},
                           base::Bind(&MigrateTaskbarPinsCallback));
}

MigrateTaskbarPinsCallback ends up calling CoCreateInstance.

0:043> kn20
 # ChildEBP RetAddr
00 2544e164 10102d0a base!base::debug::BreakDebugger+0x17
01 2544e6e8 103ae4a5 base!logging::LogMessage::~LogMessage+0x3ca
02 2544e7b4 103adb78 base!base::win::AssertComInitialized+0x95
03 2544e7bc 103c18df base!base::win::`anonymous namespace'::HookManager::DCheckedCoCreateInstance+0x8
04 2544ede0 103c16c1 base!base::win::ResolveShortcutProperties+0x14f
05 2544ef6c 06d300d5 base!base::win::ResolveShortcut+0xe1
06 2544f714 06d30b3d chrome_30d0000!shell_integration::win::MigrateShortcutsInPathInternal+0xe5
07 2544f818 03d4d066 chrome_30d0000!shell_integration::`anonymous namespace'::MigrateTaskbarPinsCallback+0xed
08 2544f820 03d4d717 chrome_30d0000!base::internal::FunctorTraits<void (__cdecl*)(void),void>::Invoke<>+0x6
09 2544f82c 03d4da95 chrome_30d0000!base::internal::InvokeHelper<0,void>::MakeItSo<void (__cdecl*const &)(void)>+0x17
0a 2544f838 03d59c34 chrome_30d0000!base::internal::Invoker<base::internal::BindState<void (__cdecl*)(void)>,void __cdecl(void)>::RunImpl<void (__cdecl*const &)(void),std::tuple<> const &>+0x15
0b 2544f854 1004ac85 chrome_30d0000!base::internal::Invoker<base::internal::BindState<void (__cdecl*)(void)>,void __cdecl(void)>::Run+0x24
0c 2544f86c 100b56ec base!base::Callback<void __cdecl(void),0,0>::Run+0x35
0d 2544f93c 1026a685 base!base::debug::TaskAnnotator::RunTask+0x1dc
0e 2544fb58 1026adfc base!base::internal::TaskTracker::PerformRunTask+0x4c5
0f 2544fce4 1025adb3 base!base::internal::TaskTracker::RunNextTask+0x15c
10 2544ff5c 1027644c base!base::internal::SchedulerWorker::Thread::ThreadMain+0x303
11 2544ff80 745b38f4 base!base::`anonymous namespace'::ThreadFunc+0xbc
12 2544ff94 76f65de3 KERNEL32!BaseThreadInitThunk+0x24
13 2544ffdc 76f65dae ntdll!__RtlUserThreadStart+0x2f
14 2544ffec 00000000 ntdll!_RtlUserThreadStart+0x1b