Get rid of two more warnings.

pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart
index 9f9ea415e093af3528dc0c4d772a87d29c5fda5e..82b942e682295b5c79cd1eaefd8d9acdc213fe33 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_library_builder.dart
@@ -347,7 +347,7 @@ class KernelLibraryBuilder
   }
 
   @override
-  void includePart(KernelLibraryBuilder part) {
+  void includePart(covariant KernelLibraryBuilder part) {

[Siggi Cherem (dart-lang), 2017/02/15 22:05:25]

happy to do it differently here, since the other covariant are still in use, we
can change them all at once.

     super.includePart(part);
     nativeMethods.addAll(part.nativeMethods);
     boundlessTypeVariables.addAll(part.boundlessTypeVariables);