Add js-interop support to the fast-startup emitter

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart b/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
index 222b1c6293fa443506a3f82cc851627a9864d6fd..3d4e9ba4fa4ccbde30f52b50d2c6c02ae2781c3e 100644
--- a/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
@@ -345,6 +345,9 @@ var #staticStateDeclaration = {};
 // Native-support uses setOrUpdateInterceptorsByTag and setOrUpdateLeafTags.
 #nativeSupport;
 
+// Sets up the js-interop support.
+#jsInteropSupport;
+
 // Invokes main (making sure that it records the 'current-script' value).
 #invokeMain;
 })()
@@ -497,6 +500,9 @@ class FragmentEmitter {
       'nativeSupport': program.needsNativeSupport
           ? emitNativeSupport(fragment)
           : new js.EmptyStatement(),
+      'jsInteropSupport': backend.jsInteropAnalysis.enabledJsInterop
+          ? backend.jsInteropAnalysis.buildJsInteropBootstrap()
+          : new js.EmptyStatement(),
       'invokeMain': fragment.invokeMain,
     });
   }