On eve only. Started a few days ago. I'm not sure why we weren't seeing this before.

 1  chrome!arc::ArcVoiceInteractionFrameworkService::OnSessionStateChanged() [arc_voice_interaction_framework_service.cc : 360 + 0x5]
 2  chrome!session_manager::SessionManager::SetSessionState(session_manager::SessionState) [session_manager.cc : 42 + 0x5]
 3  chrome!chromeos::ChromeSessionManager::SessionStarted() [chrome_session_manager.cc : 217 + 0xd]
 4  chrome!chromeos::(anonymous namespace)::StartUserSession(Profile*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) [chrome_session_manager.cc : 124 + 0x6]
 5  chrome!chromeos::ChromeSessionManager::Initialize(base::CommandLine const&, Profile*, bool) [chrome_session_manager.cc : 0 + 0x5]
 6  chrome!chromeos::ChromeBrowserMainPartsChromeos::PostProfileInit() [chrome_browser_main_chromeos.cc : 1007 + 0x7]

It's probably the ash::Shell::Get() in this code:
  // TODO( crbug.com/757012 ): Avoid using ash::Shell here so that it can work in
  // mash.
  PrefService* prefs = Profile::FromBrowserContext(context_)->GetPrefs();
  bool enabled = prefs->GetBoolean(prefs::kVoiceInteractionEnabled);
  ash::Shell::Get()->NotifyVoiceInteractionEnabled(enabled);

updowndota's CL https://chromium-review.googlesource.com/c/chromium/src/+/734126 will fix the problem for real. I'm going to add an early-exit to get the build passing while that CL is in review.