Crash in BraveProfileManager::~BraveProfileManager

[iefremov]

https://brave.sp.backtrace.io/p/brave/debug?time=month&filters=(ver%3E%3D%2293%22%2C(callstack%2Ccontains%2CBraveProfileManager)%2C_deleted%3D0%2Cptype%3Dbrowser)&debug=(%2228ea9a2%22,0,0)

[ 00 ] base::ObserverList<net::ResolveContext::DohStatusObserver, true, false, base::internal::CheckedObserverAdapter>::begin() const
[ 01 ] ProfileManager::~ProfileManager()
[ 02 ] BraveProfileManager::~BraveProfileManager()
[ 03 ] BraveProfileManager::~BraveProfileManager()
[ 04 ] BrowserProcessImpl::~BrowserProcessImpl()
[ 05 ] non-virtual thunk to BraveBrowserProcessImpl::~BraveBrowserProcessImpl()
[ 06 ] ChromeBrowserMainParts::~ChromeBrowserMainParts()
[ 07 ] ChromeBrowserMainPartsLinux::~ChromeBrowserMainPartsLinux()
[ 08 ] content::BrowserMainLoop::~BrowserMainLoop()
[ 09 ] content::BrowserMainLoop::~BrowserMainLoop()
[ 10 ] content::BrowserMainRunnerImpl::Shutdown()
[ 11 ] content::BrowserMainRunnerImpl::~BrowserMainRunnerImpl()
[ 12 ] content::BrowserMain(content::MainFunctionParams const&)
[ 13 ] content::ContentMainRunnerImpl::Run(bool)
[ 14 ] content::ContentMain(content::ContentMainParams const&)

[iefremov]

Could be connected to brave/brave-core#8124 and https://github.com/brave/brave-core/blob/db5da23611626217061c8a6792678639cb716c3d/browser/brave_shields/ad_block_subscription_download_manager_getter.cc#L92 (first crashes started to appear around date of merging that PR)

it looks like ProfileManager tries to delete an observer that wasnt removed

cc @bridiver @antonok-edm