After adding logic to catch previously swallowed exceptions in json_rpc_2, we're now seeing this exception thrown in devicelab and google3 tests.

JSON-RPC error -32601 (method not found): Unknown method "streamNotify".
#0      Server._tryFallbacks._tryNext (package:json_rpc_2/src/server.dart:272:9)
<asynchronous suspension>
#1      Server._tryFallbacks (package:json_rpc_2/src/server.dart:284:20)

I suspect this is a timing issue where something is trying to call that method before we've registered it - it gets registered in https://github.com/flutter/flutter/blob/master/packages/flutter_tools/lib/src/vmservice.dart#L113