My recent changes have revealed a number of errors in USS DeviceInfo:

https://uma.googleplex.com/p/chrome/timeline_v2/?sid=0f070dccf97e6ea8f09ad2609c9191db

It appears these are due to an unexpectedly high rate of failure creating the ModelTypeStore. We should fix this in M57 beta, or we shouldn't roll out USS to M57 stable. Sample stack dumps:

https://crash.corp.google.com/browse?q=ReportID%3D%271f4f384680000000
https://crash.corp.google.com/browse?q=ReportID%3D%27c135ad8680000000

0x000007feea6ad5d3	(chrome_elf.dll -crashpad_win.cc:155 )	DumpProcessWithoutCrash
0x000007fee97328cc	(chrome.dll -report_unrecoverable_error.cc:27 )	syncer::ReportUnrecoverableError(version_info::Channel)
0x000007fee9ba255e	(chrome.dll -shared_model_type_processor.cc:154 )	syncer::SharedModelTypeProcessor::ReportError(syncer::ModelError const &)
0x000007fee9ba25e5	(chrome.dll -shared_model_type_processor.cc:170 )	syncer::SharedModelTypeProcessor::ReportError(tracked_objects::Location const &,std::basic_string<char,std::char_traits<char>,std::allocator<char> > const &)
0x000007fee9b94e19	(chrome.dll -device_info_sync_bridge.cc:346 )	syncer::DeviceInfoSyncBridge::OnStoreCreated(syncer::ModelTypeStore::Result,std::unique_ptr<syncer::ModelTypeStore,std::default_delete<syncer::ModelTypeStore> >)
0x000007fee7df10ff	(chrome.dll -bind_internal.h:339 )	base::internal::Invoker<base::internal::BindState<void ( content::ServiceWorkerControlleeRequestHandler::*)(content::ServiceWorkerStatusCode,scoped_refptr<content::ServiceWorkerRegistration>),base::WeakPtr<content::ServiceWorkerControlleeRequestHandler> >,void >::Run(base::internal::BindStateBase *,content::ServiceWorkerStatusCode &&,scoped_refptr<content::ServiceWorkerRegistration> &&)
0x000007fee9ba6abf	(chrome.dll -model_type_store_impl.cc:148 )	syncer::ModelTypeStoreImpl::BackendInitDone(syncer::ModelType,std::unique_ptr<syncer::ModelTypeStore::Result,std::default_delete<syncer::ModelTypeStore::Result> >,scoped_refptr<base::SequencedTaskRunner>,base::Callback<void ,1,1> const &,scoped_refptr<syncer::ModelTypeStoreBackend>)
0x000007fee9ba8d3f	(chrome.dll -bind_internal.h:339 )	base::internal::Invoker<base::internal::BindState<void (*)(syncer::ModelType,std::unique_ptr<syncer::ModelTypeStore::Result,std::default_delete<syncer::ModelTypeStore::Result> >,scoped_refptr<base::SequencedTaskRunner>,base::Callback<void ,1,1> const &,scoped_refptr<syncer::ModelTypeStoreBackend>),syncer::ModelType,base::internal::PassedWrapper<std::unique_ptr<syncer::ModelTypeStore::Result,std::default_delete<syncer::ModelTypeStore::Result> > >,scoped_refptr<base::SequencedTaskRunner>,base::Callback<void ,1,1> >,void >::Run(base::internal::BindStateBase *,scoped_refptr<syncer::ModelTypeStoreBackend> &&)
0x000007fee9ba88cb	(chrome.dll -post_task_and_reply_with_result_internal.h:28 )	base::internal::ReplyAdapter<scoped_refptr<syncer::ModelTypeStoreBackend>,scoped_refptr<syncer::ModelTypeStoreBackend> >(base::Callback<void ,1,1> const &,scoped_refptr<syncer::ModelTypeStoreBackend> *)
0x000007fee820acb0	(chrome.dll -post_task_and_reply_impl.cc:61 )	base::`anonymous namespace'::PostTaskAndReplyRelay::RunReplyAndSelfDestruct
0x000007fee7c1c523	(chrome.dll -callback.h:68 )	base::internal::RunMixin<base::Callback<void ,0,0> >::Run( ?? )
0x000007fee821b711	(chrome.dll -task_annotator.cc:52 )	base::debug::TaskAnnotator::RunTask(char const *,base::PendingTask *)
0x000007fee81c9473	(chrome.dll -message_loop.cc:421 )	base::MessageLoop::RunTask(base::PendingTask *)
0x000007fee81ca0b4	(chrome.dll -message_loop.cc:523 )	base::MessageLoop::DoWork()
0x000007fee821bd10	(chrome.dll -message_pump_win.cc:173 )	base::MessagePumpForUI::DoRunLoop()
0x000007fee821b943	(chrome.dll -message_pump_win.cc:56 )	base::MessagePumpWin::Run(base::MessagePump::Delegate *)
0x000007fee81f2753	(chrome.dll -run_loop.cc:37 )	base::RunLoop::Run()