We collected slow reports from users facing janks and found that the function mentioned above is taking too much time on the main thread, potentially causing janks at startup.
The issue can be found in reports:
84d831b7f1f69cfa
7557f2da18e748b6
4235fd6bf348196a
6e608ee54638435b
d928a79ace8f7a2f
3c31f13114f9f68b
9c11a38ac9cfc67c
59a0097389e81c81
0b0320f2bd8ab4df

Go to crash/ReportID to view the traces.

The stack trace that was hit the most:
Unknown
icu_62::UnicodeSet::add(int const*, int, signed char)
icu_62::UnicodeSet::add(int, int)
icu_62::UnicodeSet::applyFilter(signed char (*)(int, void*), void*, int, UErrorCode&)
icu_62::UnicodeSet::applyIntPropertyValue(UProperty, int, UErrorCode&)
icu_62::UnicodeSet::applyPropertyAlias(icu_62::UnicodeString const&, icu_62::UnicodeString const&, UErrorCode&)
icu_62::UnicodeSet::applyPropertyPattern(icu_62::UnicodeString const&, icu_62::ParsePosition&, UErrorCode&)
icu_62::UnicodeSet::applyPropertyPattern(icu_62::RuleCharacterIterator&, icu_62::UnicodeString&, UErrorCode&)
icu_62::UnicodeSet::applyPattern(icu_62::RuleCharacterIterator&, icu_62::SymbolTable const*, icu_62::UnicodeString&, unsigned int, icu_62::UnicodeSet& (icu_62::UnicodeSet::*)(int), int, UErrorCode&)
icu_62::UnicodeSet::applyPatternIgnoreSpace(icu_62::UnicodeString const&, icu_62::ParsePosition&, icu_62::SymbolTable const*, UErrorCode&)
icu_62::UnicodeSet::applyPattern(icu_62::UnicodeString const&, UErrorCode&)
icu_62::UnicodeSet::UnicodeSet(icu_62::UnicodeString const&, UErrorCode&)
icu_62::RegexStaticSets::RegexStaticSets(UErrorCode*)
icu_62::initStaticSets(UErrorCode&)
icu_62::umtx_initOnce(icu_62::UInitOnce&, void (*)(UErrorCode&), UErrorCode&)
icu_62::RegexCompile::RegexCompile(icu_62::RegexPattern*, UErrorCode&)
icu_62::RegexPattern::compile(icu_62::UnicodeString const&, unsigned int, UParseError&, UErrorCode&)
icu_62::RegexMatcher::RegexMatcher(icu_62::UnicodeString const&, unsigned int, UErrorCode&)
policy::BrowserPolicyConnector::IsNonEnterpriseUser(std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> > const&)
policy::UserPolicySigninServiceBase::ShouldLoadPolicyForUser(std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> > const&)
policy::UserPolicySigninServiceBase::InitializeForSignedInUser(AccountId const&, scoped_refptr<network::SharedURLLoaderFactory>)
policy::UserPolicySigninServiceBase::InitializeOnProfileReady(Profile*)
content::NotificationServiceImpl::Notify(int, content::NotificationSource const&, content::NotificationDetails const&)
ProfileManager::DoFinalInit(Profile*, bool)
ProfileManager::AddProfile(Profile*)
ProfileManager::CreateAndInitializeProfile(base::FilePath const&)
ProfileManager::GetProfile(base::FilePath const&)
ProfileManager::CreateInitialProfile()
ChromeBrowserMainParts::PreMainMessageLoopRunImpl()
ChromeBrowserMainParts::PreMainMessageLoopRun()
content::BrowserMainLoop::PreMainMessageLoopRun()
int base::internal::Invoker<base::internal::BindState<int (content::BrowserMainLoop::*)(), base::internal::UnretainedWrapper<content::BrowserMainLoop> >, int ()>::RunImpl<int (content::BrowserMainLoop::* const&)(), std::__ndk1::tuple<base::internal::UnretainedWrapper<content::BrowserMainLoop> > const&, 0u>(int (content::BrowserMainLoop::* const&&&)(), std::__ndk1::tuple<base::internal::UnretainedWrapper<content::BrowserMainLoop> > const&&&, std::__ndk1::integer_sequence<unsigned int, 0u>)
content::StartupTaskRunner::WrappedTask()
void base::internal::Invoker<base::internal::BindState<void (net::DnsConfigService::*)(), base::internal::UnretainedWrapper<net::DnsConfigService> >, void ()>::RunImpl<void (net::DnsConfigService::*)(), std::__ndk1::tuple<base::internal::UnretainedWrapper<net::DnsConfigService> >, 0u>(void (net::DnsConfigService::*&&)(), std::__ndk1::tuple<base::internal::UnretainedWrapper<net::DnsConfigService> >&&, std::__ndk1::integer_sequence<unsigned int, 0u>)
base::debug::TaskAnnotator::RunTask(char const*, base::PendingTask*)
base::MessageLoop::RunTask(base::PendingTask*)
base::MessageLoop::DoWork()
base::MessagePumpForUI::OnNonDelayedLooperCallback()
base::(anonymous namespace)::NonDelayedLooperCallback(int, int, void*)