Fix error handling in dart2js async-await

pkg/compiler/lib/src/js_backend/backend.dart

Index: pkg/compiler/lib/src/js_backend/backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend.dart b/pkg/compiler/lib/src/js_backend/backend.dart
index e39689912d640397e5d405738780373d805b89af..96d94e76e89a3c9d5d1d975ae7721d1665d18b83 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -1600,8 +1600,8 @@ class JavaScriptBackend extends Backend {
     return findHelper("throwCyclicInit");
   }
 
-  Element getThenHelper() {
-    return findHelper("thenHelper");
+  Element getAsyncHelper() {
+    return findHelper("asyncHelper");
   }
 
   Element getYieldStar() {
@@ -1616,8 +1616,8 @@ class JavaScriptBackend extends Backend {
     return classElement.lookupLocalMember("yieldSingle");
   }
 
-  Element getStreamHelper() {
-    return findHelper("streamHelper");
+  Element getAsyncStarHelper() {
+    return findHelper("asyncStarHelper");
   }
 
   Element getStreamOfController() {
@@ -2405,7 +2405,7 @@ class JavaScriptBackend extends Backend {
                            Enqueuer enqueuer,
                            Registry registry) {
     if (element.asyncMarker == AsyncMarker.ASYNC) {
-      enqueue(enqueuer, getThenHelper(), registry);
+      enqueue(enqueuer, getAsyncHelper(), registry);
       enqueue(enqueuer, getCompleterConstructor(), registry);
       enqueue(enqueuer, getStreamIteratorConstructor(), registry);
     } else if (element.asyncMarker == AsyncMarker.SYNC_STAR) {
@@ -2415,7 +2415,7 @@ class JavaScriptBackend extends Backend {
       enqueue(enqueuer, getYieldStar(), registry);
     } else if (element.asyncMarker == AsyncMarker.ASYNC_STAR) {
       enqueuer.registerInstantiatedClass(getASyncStarController(), registry);
-      enqueue(enqueuer, getStreamHelper(), registry);
+      enqueue(enqueuer, getAsyncStarHelper(), registry);
       enqueue(enqueuer, getStreamOfController(), registry);
       enqueue(enqueuer, getYieldSingle(), registry);
       enqueue(enqueuer, getYieldStar(), registry);