Fix Array constructor bug impacting dart2js and ddc running on the same page.

lib/src/codegen/js_codegen.dart

Index: lib/src/codegen/js_codegen.dart
diff --git a/lib/src/codegen/js_codegen.dart b/lib/src/codegen/js_codegen.dart
index 85b42aa56d42f9ca351932e4bee14d862c65b40a..b574bcf1550f2d1c3559b5a6da22a39adfbe8998 100644
--- a/lib/src/codegen/js_codegen.dart
+++ b/lib/src/codegen/js_codegen.dart
@@ -357,7 +357,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
         // want to support construction of instances with generic types other
         // than dynamic. See issue #154 for Array and List<E> related bug.
         var copyMembers = js.statement(
-            'dart.copyProperties(dart.global.#.prototype, #.prototype);', [
+            'dart.registerExtension(dart.global.#, #);', [
           _propertyName(jsPeerName),
           classElem.name
         ]);