fixes browser/runtime_test, and a few extension member fixes

lib/runtime/dart/_js_helper.js

 var _js_helper = dart.defineLibrary(_js_helper, {});
 var core = dart.import(core);
 var collection = dart.import(collection);
 var _internal = dart.import(_internal);
 var _foreign_helper = dart.import(_foreign_helper);
 var _interceptors = dart.lazyImport(_interceptors);
 var _js_names = dart.import(_js_names);
 var _js_embedded_names = dart.import(_js_embedded_names);
 var async = dart.import(async);
 var _isolate_helper = dart.lazyImport(_isolate_helper);
@@ skipping 209 matching lines @@
       get iterator() {
         return this[_map][_keys][dartx.iterator];
       }
       get length() {
         return this[_map][_keys].length;
       }
     }
     dart.setSignature(_ConstantMapKeyIterable, {
       constructors: () => ({_ConstantMapKeyIterable: [_ConstantMapKeyIterable$(K), [ConstantStringMap$(K, core.Object)]]})
     });
+    dart.defineExtensionMembers(_ConstantMapKeyIterable, ['iterator', 'length']);
     return _ConstantMapKeyIterable;
   });
   let _ConstantMapKeyIterable = _ConstantMapKeyIterable$();
   let _jsData = Symbol('_jsData');
   let _getMap = Symbol('_getMap');
   let GeneralConstantMap$ = dart.generic(function(K, V) {
     class GeneralConstantMap extends ConstantMap$(K, V) {
       GeneralConstantMap(jsData) {
         this[_jsData] = jsData;
         super._();
@@ skipping 201 matching lines @@
       return this[_execAnchored](string, start);
     }
     get isMultiLine() {
       return this[_isMultiLine];
     }
     get isCaseSensitive() {
       return this[_isCaseSensitive];
     }
   }
   JSSyntaxRegExp[dart.implements] = () => [core.RegExp];
-  dart.defineExtensionMembers(JSSyntaxRegExp, ['allMatches', 'matchAsPrefix']);
   dart.setSignature(JSSyntaxRegExp, {
     constructors: () => ({JSSyntaxRegExp: [JSSyntaxRegExp, [core.String], {multiLine: core.bool, caseSensitive: core.bool}]}),
     methods: () => ({
       firstMatch: [core.Match, [core.String]],
       hasMatch: [core.bool, [core.String]],
       stringMatch: [core.String, [core.String]],
       allMatches: [core.Iterable$(core.Match), [core.String], [core.int]],
       [_execGlobal]: [core.Match, [core.String, core.int]],
       [_execAnchored]: [core.Match, [core.String, core.int]],
       matchAsPrefix: [core.Match, [core.String], [core.int]]
     }),
     statics: () => ({makeNative: [core.Object, [core.String, core.bool, core.bool, core.bool]]}),
     names: ['makeNative']
   });
+  dart.defineExtensionMembers(JSSyntaxRegExp, ['allMatches', 'matchAsPrefix']);
   let _match = Symbol('_match');
   class _MatchImplementation extends core.Object {
     _MatchImplementation(pattern, match) {
       this.pattern = pattern;
       this[_match] = match;
       dart.assert(typeof this[_match].input == 'string');
       dart.assert(typeof this[_match].index == 'number');
     }
     get input() {
       return this[_match].input;
@@ skipping 40 matching lines @@
       this[_start] = start;
       super.IterableBase();
     }
     get iterator() {
       return new _AllMatchesIterator(this[_re], this[_string], this[_start]);
     }
   }
   dart.setSignature(_AllMatchesIterable, {
     constructors: () => ({_AllMatchesIterable: [_AllMatchesIterable, [JSSyntaxRegExp, core.String, core.int]]})
   });
+  dart.defineExtensionMembers(_AllMatchesIterable, ['iterator']);
   let _regExp = Symbol('_regExp');
   let _nextIndex = Symbol('_nextIndex');
   let _current = Symbol('_current');
   class _AllMatchesIterator extends core.Object {
     _AllMatchesIterator(regExp, string, nextIndex) {
       this[_regExp] = regExp;
       this[_string] = string;
       this[_nextIndex] = nextIndex;
       this[_current] = null;
     }
@@ skipping 3618 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, core, collection, _internal, _foreign_helper, _interceptors, _js_names, _js_embedded_names, async, _isolate_helper);