SDK fixes

lib/runtime/dart/_js_helper.js

 var _js_helper;
 (function(exports) {
   'use strict';
   class NoSideEffects extends core.Object {
     NoSideEffects() {
     }
   }
   class NoThrows extends core.Object {
     NoThrows() {
     }
@@ skipping 33 matching lines @@
         dart.as(key, K);
         dart.as(val, V);
         return this[_throwUnmodifiable]();
       }
       putIfAbsent(key, ifAbsent) {
         dart.as(key, K);
         dart.as(ifAbsent, dart.functionType(V, []));
         return dart.as(this[_throwUnmodifiable](), V);
       }
       remove(key) {
-        dart.as(key, K);
         return dart.as(this[_throwUnmodifiable](), V);
       }
       clear() {
         return this[_throwUnmodifiable]();
       }
       addAll(other) {
         dart.as(other, core.Map$(K, V));
         return this[_throwUnmodifiable]();
       }
     }
     ConstantMap[dart.implements] = () => [core.Map$(K, V)];
     dart.defineNamedConstructor(ConstantMap, '_');
     return ConstantMap;
   });
   let ConstantMap = ConstantMap$();
   let _jsObject = Symbol('_jsObject');
   let _keys = Symbol('_keys');
   let _fetch = Symbol('_fetch');
   let ConstantStringMap$ = dart.generic(function(K, V) {
     class ConstantStringMap extends ConstantMap$(K, V) {
       _(length, jsObject, keys) {
         this.length = length;
         this[_jsObject] = jsObject;
         this[_keys] = keys;
         super._();
       }
       containsValue(needle) {
-        dart.as(needle, V);
         return this.values[core.$any](value => dart.equals(value, needle));
       }
       containsKey(key) {
         if (!(typeof key == 'string'))
           return false;
         if (dart.equals('__proto__', key))
           return false;
         return jsHasOwnProperty(this[_jsObject], dart.as(key, core.String));
       }
       get(key) {
@@ skipping 69 matching lines @@
     class GeneralConstantMap extends ConstantMap$(K, V) {
       GeneralConstantMap(jsData) {
         this[_jsData] = jsData;
         super._();
       }
       [_getMap]() {
         if (!this.$map) {
           let backingMap = new (collection.LinkedHashMap$(K, V))();
           this.$map = fillLiteralMap(this[_jsData], backingMap);
         }
-        return this.$map;
+        return dart.as(this.$map, core.Map$(K, V));
       }
       containsValue(needle) {
-        dart.as(needle, V);
         return this[_getMap]().containsValue(needle);
       }
       containsKey(key) {
         return this[_getMap]().containsKey(key);
       }
       get(key) {
         return this[_getMap]().get(key);
       }
       forEach(f) {
         dart.as(f, dart.functionType(dart.void, [K, V]));
@@ skipping 3887 matching lines @@
   exports.jsonEncodeNative = jsonEncodeNative;
   exports.getIsolateAffinityTag = getIsolateAffinityTag;
   exports.LoadLibraryFunctionType = LoadLibraryFunctionType;
   exports.DeferredLoadCallback = DeferredLoadCallback;
   exports.loadDeferredLibrary = loadDeferredLibrary;
   exports.MainError = MainError;
   exports.missingMain = missingMain;
   exports.badMain = badMain;
   exports.mainHasTooManyParameters = mainHasTooManyParameters;
 })(_js_helper || (_js_helper = {}));