fuse List and js Array together and a few other misc fixes.

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 d81ba2aa6ca13b7cc9a0c53437f9883aeb0331c1..8e6ca14d2e2a31e24b31a485aa64a6a2b4dd30dd 100644
--- a/lib/runtime/dart_runtime.js
+++ b/lib/runtime/dart_runtime.js
@@ -9,6 +9,7 @@ var dart, _js_helper;
   let defineProperty = Object.defineProperty;
   let getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor;
   let getOwnPropertyNames = Object.getOwnPropertyNames;
+  let getOwnPropertySymbols = Object.getOwnPropertySymbols;
 
   // Adapted from Angular.js
   let FN_ARGS = /^function\s*[^\(]*\(\s*([^\)]*)\)/m;
@@ -614,11 +615,14 @@ var dart, _js_helper;
    * This operation is commonly called `mixin` in JS.
    */
   function copyProperties(to, from) {
-    let names = getOwnPropertyNames(from);
-    for (let i = 0; i < names.length; i++) {
-      let name = names[i];
-      defineProperty(to, name, getOwnPropertyDescriptor(from, name));
+    function copyPropertiesHelper(names) {
+      for (let i = 0; i < names.length; i++) {
+        let name = names[i];
+        defineProperty(to, name, getOwnPropertyDescriptor(from, name));
+      }
     }
+    copyPropertiesHelper(getOwnPropertyNames(from));
+    copyPropertiesHelper(getOwnPropertySymbols(from));
     return to;
   }
   dart.copyProperties = copyProperties;