Remove (for the time being) async-await from dart2js.

pkg/compiler/lib/src/library_loader.dart

Index: pkg/compiler/lib/src/library_loader.dart
diff --git a/pkg/compiler/lib/src/library_loader.dart b/pkg/compiler/lib/src/library_loader.dart
index 3e6acb5b93c15dbe34145ddb44d5655620a1b801..2a5a413aa4f0f200d149f0ff96fa0b22b41bbf1d 100644
--- a/pkg/compiler/lib/src/library_loader.dart
+++ b/pkg/compiler/lib/src/library_loader.dart
@@ -533,12 +533,12 @@ class _LibraryLoaderTask extends CompilerTask implements LibraryLoaderTask {
       LibraryElement library) async {

[Siggi Cherem (dart-lang), 2015/07/23 00:03:06]

might be good to remove `async` as well to avoid confusion.

     compiler.onLibraryCreated(library);
     libraryCanonicalUriMap[library.canonicalUri] = library;
-    await compiler.onLibraryScanned(library, handler);
-    for (LibraryTag tag in library.tags) {
-      LibraryElement dependency = library.getLibraryFromTag(tag);
-      await createLibrary(handler, library, dependency.canonicalUri);
-    }
-    return library;
+    return compiler.onLibraryScanned(library, handler).then((_) {
+      return future.forEach(library.tags, (LibraryTag tag) {
+        LibraryElement dependency = library.getLibraryFromTag(tag);
+        return createLibrary(handler, library, dependency.canonicalUri);
+      }).then((_) => library);
+    });
   }
 
   /**