Fix TODO in polymer _shimCss, remove package:js dependency

pkg/polymer/lib/src/transform/polyfill_injector.dart

Index: pkg/polymer/lib/src/transform/polyfill_injector.dart
diff --git a/pkg/polymer/lib/src/transform/polyfill_injector.dart b/pkg/polymer/lib/src/transform/polyfill_injector.dart
index c80438846762903596d61d2379942169405f6519..1e62173f0da201590bf3e8d56abbb35a70d2745c 100644
--- a/pkg/polymer/lib/src/transform/polyfill_injector.dart
+++ b/pkg/polymer/lib/src/transform/polyfill_injector.dart
@@ -34,7 +34,6 @@ class PolyfillInjector extends Transformer with PolymerTransformer {
     return readPrimaryAsHtml(transform).then((document) {
       bool shadowDomFound = false;
       bool jsInteropFound = false;
-      bool pkgJsInteropFound = false;
       bool dartScriptTags = false;
 
       for (var tag in document.queryAll('script')) {
@@ -43,8 +42,6 @@ class PolyfillInjector extends Transformer with PolymerTransformer {
           var last = src.split('/').last;
           if (last == 'interop.js') {
             jsInteropFound = true;
-          } else if (last == 'dart_interop.js') {
-            pkgJsInteropFound = true;
           } else if (_shadowDomJS.hasMatch(last)) {
             shadowDomFound = true;
           }
@@ -61,12 +58,6 @@ class PolyfillInjector extends Transformer with PolymerTransformer {
         return;
       }
 
-      if (!pkgJsInteropFound) {
-        // JS interop code is required for Polymer CSS shimming.
-        document.body.nodes.insert(0, parseFragment(
-            '<script src="packages/js/dart_interop.js"></script>\n'));
-      }
-
       if (!jsInteropFound) {
         // JS interop code is required for Polymer CSS shimming.
         document.body.nodes.insert(0, parseFragment(