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

lib/runtime/dart_runtime.js

Index: lib/runtime/dart_runtime.js
diff --git a/lib/runtime/dart_runtime.js b/lib/runtime/dart_runtime.js
index 01791fdc06a5c9cc1c9e6bc0251e7edd0d6cdf44..05ad75613f0c1a6197ac0ee22810c1cffb823d80 100644
--- a/lib/runtime/dart_runtime.js
+++ b/lib/runtime/dart_runtime.js
@@ -611,17 +611,33 @@ var dart, _js_helper;
   dart.defineLazyProperties = defineLazy;
   dart.defineLazyClassGeneric = defineLazyProperty;
 
+  function copyPropertiesHelper(to, from, names) {

[Jennifer Messerly, 2015/04/23 19:33:53]

hmm, not sure this is really worth a helper.

+    for (let name of names) {
+      defineProperty(to, name, getOwnPropertyDescriptor(from, name));
+    }
+    return to;
+  }
+
   /**
    * Copy properties from source to destination object.
    * This operation is commonly called `mixin` in JS.
    */
   function copyProperties(to, from) {
-    for (let name of getOwnNamesAndSymbols(from)) {
-      defineProperty(to, name, getOwnPropertyDescriptor(from, name));
-    }
-    return to;
+    return copyPropertiesHelper(to, from,
+        getOwnNamesAndSymbols(from));

[Jennifer Messerly, 2015/04/23 19:33:53]

short line? it looks like it would fit

   }
+
+  /**
+   * Copy symbols from source to destination object.
+   * These are the only properties safe to copy onto an existing public
+   * JavaScript class.
+   */
+  function copyPropertySymbols(to, from) {
+    return copyPropertiesHelper(to, from, getOwnPropertySymbols(from));
+  }
+
   dart.copyProperties = copyProperties;
+  dart.copyPropertySymbols = copyPropertySymbols;
 
   /**
    * This is called whenever a derived class needs to introduce a new field,