Allow import/export of libraries with no name.

sdk/lib/_internal/compiler/implementation/library_loader.dart

Index: sdk/lib/_internal/compiler/implementation/library_loader.dart
diff --git a/sdk/lib/_internal/compiler/implementation/library_loader.dart b/sdk/lib/_internal/compiler/implementation/library_loader.dart
index be9e3b76a8ca713d9de25f05feb19ecfb5fba9c1..1342ce8cbe080f457dcb87324ba557ead384517b 100644
--- a/sdk/lib/_internal/compiler/implementation/library_loader.dart
+++ b/sdk/lib/_internal/compiler/implementation/library_loader.dart
@@ -421,15 +421,6 @@ class LibraryLoaderTask extends LibraryLoader {
           if (loadedLibrary == null) return;
           compiler.withCurrentElement(library, () {
             handler.registerDependency(library, tag, loadedLibrary);
-
-            if (!loadedLibrary.hasLibraryName()) {
-              compiler.reportFatalError(
-                  tag == null ? null : tag.uri,
-                  MessageKind.GENERIC,
-                  {'text':
-                   'Error: No library name found in '
-                      '${loadedLibrary.canonicalUri}.'});
-            }
           });
         });
   }