fixes browser/runtime_test, and a few extension member fixes

lib/runtime/dart/_js_helper.js

Index: lib/runtime/dart/_js_helper.js
diff --git a/lib/runtime/dart/_js_helper.js b/lib/runtime/dart/_js_helper.js
index b8873d8f3a4e4901e3f834cc151f3664ca90f7da..c498ba7f152a5d012b49cc61452cc4dd2da13a1c 100644
--- a/lib/runtime/dart/_js_helper.js
+++ b/lib/runtime/dart/_js_helper.js
@@ -227,6 +227,7 @@ var _isolate_helper = dart.lazyImport(_isolate_helper);
     dart.setSignature(_ConstantMapKeyIterable, {
       constructors: () => ({_ConstantMapKeyIterable: [_ConstantMapKeyIterable$(K), [ConstantStringMap$(K, core.Object)]]})
     });
+    dart.defineExtensionMembers(_ConstantMapKeyIterable, ['iterator', 'length']);
     return _ConstantMapKeyIterable;
   });
   let _ConstantMapKeyIterable = _ConstantMapKeyIterable$();
@@ -448,7 +449,6 @@ var _isolate_helper = dart.lazyImport(_isolate_helper);
     }
   }
   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: () => ({
@@ -463,6 +463,7 @@ var _isolate_helper = dart.lazyImport(_isolate_helper);
     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) {
@@ -523,6 +524,7 @@ var _isolate_helper = dart.lazyImport(_isolate_helper);
   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');