fix some errors in our SDK, mostly around numbers

lib/runtime/dart/_js_helper.js

 dart_library.library('dart/_js_helper', null, /* Imports */[
   "dart_runtime/dart",
   'dart/core',
   'dart/collection',
   'dart/_interceptors',
   'dart/_foreign_helper'
 ], /* Lazy imports */[
 ], function(exports, dart, core, collection, _interceptors, _foreign_helper) {
   'use strict';
   let dartx = dart.dartx;
@@ skipping 676 matching lines @@
       return result;
     }
     static stringFromCodePoints(codePoints) {
       let a = dart.list([], core.int);
       for (let i of dart.as(codePoints, core.Iterable)) {
         if (!(typeof i == 'number'))
           dart.throw(new core.ArgumentError(i));
         if (dart.notNull(dart.as(dart.dsend(i, '<=', 65535), core.bool))) {
           a[dartx.add](dart.as(i, core.int));
         } else if (dart.notNull(dart.as(dart.dsend(i, '<=', 1114111), core.bool))) {
-          a[dartx.add]((55296)[dartx['+']](dart.as(dart.dsend(dart.dsend(dart.dsend(i, '-', 65536), '>>', 10), '&', 1023), core.num)));
-          a[dartx.add]((56320)[dartx['+']](dart.as(dart.dsend(i, '&', 1023), core.num)));
+          a[dartx.add](dart.asInt((55296)[dartx['+']](dart.as(dart.dsend(dart.dsend(dart.dsend(i, '-', 65536), '>>', 10), '&', 1023), core.num))));
+          a[dartx.add](dart.asInt((56320)[dartx['+']](dart.as(dart.dsend(i, '&', 1023), core.num))));
         } else {
           dart.throw(new core.ArgumentError(i));
         }
       }
       return Primitives._fromCharCodeApply(a);
     }
     static stringFromCharCodes(charCodes) {
       for (let i of dart.as(charCodes, core.Iterable)) {
         if (!(typeof i == 'number'))
           dart.throw(new core.ArgumentError(i));
@@ skipping 106 matching lines @@
     }
     static valueFromDateString(str) {
       if (!(typeof str == 'string'))
         dart.throw(new core.ArgumentError(str));
       let value = Date.parse(str);
       if (dart.notNull(value[dartx.isNaN]))
         dart.throw(new core.ArgumentError(str));
       return value;
     }
     static getProperty(object, key) {
-      if (object == null || typeof object == 'boolean' || dart.is(object, core.num) || typeof object == 'string') {
+      if (object == null || typeof object == 'boolean' || typeof object == 'number' || typeof object == 'string') {
         dart.throw(new core.ArgumentError(object));
       }
       return object[key];
     }
     static setProperty(object, key, value) {
-      if (object == null || typeof object == 'boolean' || dart.is(object, core.num) || typeof object == 'string') {
+      if (object == null || typeof object == 'boolean' || typeof object == 'number' || typeof object == 'string') {
         dart.throw(new core.ArgumentError(object));
       }
       object[key] = value;
     }
     static identicalImplementation(a, b) {
       return a == null ? b == null : a === b;
     }
     static extractStackTrace(error) {
       return getTraceFromException(error.$thrownJsError);
     }
   }
   dart.setSignature(Primitives, {
     statics: () => ({
       initializeStatics: [dart.void, [core.int]],
       objectHashCode: [core.int, [dart.dynamic]],
       _throwFormatException: [dart.dynamic, [core.String]],
       parseInt: [core.int, [core.String, core.int, dart.functionType(core.int, [core.String])]],
       parseDouble: [core.double, [core.String, dart.functionType(core.double, [core.String])]],
       objectTypeName: [core.String, [core.Object]],
       objectToString: [core.String, [core.Object]],
-      dateNow: [core.num, []],
+      dateNow: [core.int, []],
       initTicker: [dart.void, []],
       currentUri: [core.String, []],
       _fromCharCodeApply: [core.String, [core.List$(core.int)]],
       stringFromCodePoints: [core.String, [dart.dynamic]],
       stringFromCharCodes: [core.String, [dart.dynamic]],
       stringFromCharCode: [core.String, [dart.dynamic]],
       stringConcatUnchecked: [core.String, [core.String, core.String]],
       flattenString: [core.String, [core.String]],
       getTimeZoneName: [core.String, [dart.dynamic]],
       getTimeZoneOffsetInMinutes: [core.int, [dart.dynamic]],
@@ skipping 25 matching lines @@
     return receiver.lastIndexOf(element, start);
   }
   dart.fn(stringLastIndexOfUnchecked);
   function checkNull(object) {
     if (object == null)
       dart.throw(new core.ArgumentError(null));
     return object;
   }
   dart.fn(checkNull);
   function checkNum(value) {
-    if (!dart.is(value, core.num)) {
+    if (!(typeof value == 'number')) {
       dart.throw(new core.ArgumentError(value));
     }
     return value;
   }
   dart.fn(checkNum);
   function checkInt(value) {
     if (!(typeof value == 'number')) {
       dart.throw(new core.ArgumentError(value));
     }
     return value;
@@ skipping 333 matching lines @@
   exports.CastErrorImplementation = CastErrorImplementation;
   exports.FallThroughErrorImplementation = FallThroughErrorImplementation;
   exports.RuntimeError = RuntimeError;
   exports.random64 = random64;
   exports.jsonEncodeNative = jsonEncodeNative;
   exports.SyncIterator$ = SyncIterator$;
   exports.SyncIterator = SyncIterator;
   exports.SyncIterable$ = SyncIterable$;
   exports.SyncIterable = SyncIterable;
 });