fix some errors in our SDK, mostly around numbers

lib/runtime/dart/_isolate_helper.js

 dart_library.library('dart/_isolate_helper', null, /* Imports */[
   "dart_runtime/dart",
   'dart/core',
   'dart/_interceptors',
   'dart/_js_helper',
   'dart/isolate',
   'dart/_foreign_helper',
   'dart/collection',
   'dart/async'
 ], /* Lazy imports */[
@@ skipping 63 matching lines @@
       if (message === void 0)
         message = null;
       if (message == null)
         message = "Can't transmit:";
       dart.throw(new core.UnsupportedError(`${message} ${x}`));
     }
     makeRef(serializationId) {
       return ["ref", serializationId];
     }
     isPrimitive(x) {
-      return x == null || typeof x == 'string' || dart.is(x, core.num) || typeof x == 'boolean';
+      return x == null || typeof x == 'string' || typeof x == 'number' || typeof x == 'boolean';
     }
     serializePrimitive(primitive) {
       return primitive;
     }
     serializeByteBuffer(buffer) {
       return ["buffer", buffer];
     }
     serializeTypedData(data) {
       return ["typed", data];
     }
@@ skipping 159 matching lines @@
         {
           return this.deserializeDartObject(x);
         }
         default:
         {
           dart.throw(`couldn't deserialize: ${x}`);
         }
       }
     }
     isPrimitive(x) {
-      return x == null || typeof x == 'string' || dart.is(x, core.num) || typeof x == 'boolean';
+      return x == null || typeof x == 'string' || typeof x == 'number' || typeof x == 'boolean';
     }
     deserializePrimitive(x) {
       return x;
     }
     deserializeRef(x) {
       dart.assert(dart.equals(dart.dindex(x, 0), 'ref'));
       let serializationId = dart.as(dart.dindex(x, 1), core.int);
       return this.deserializedObjects[dartx.get](serializationId);
     }
     deserializeByteBuffer(x) {
@@ skipping 1285 matching lines @@
   exports.leaveJsAsync = leaveJsAsync;
   exports.isWorker = isWorker;
   exports.startRootIsolate = startRootIsolate;
   exports.IsolateNatives = IsolateNatives;
   exports.RawReceivePortImpl = RawReceivePortImpl;
   exports.ReceivePortImpl = ReceivePortImpl;
   exports.TimerImpl = TimerImpl;
   exports.hasTimer = hasTimer;
   exports.CapabilityImpl = CapabilityImpl;
 });