Reduce strong mode errors and warnings

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

Index: pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
index 851c4563e4c8d55f155f8ff96119c15a2a2a7082..f9134d9197328ea3202cc927c186d771050444b2 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
@@ -51,7 +51,6 @@ import 'kernel_builder.dart' show
     KernelProcedureBuilder,
     KernelTypeBuilder,
     LibraryBuilder,
-    MemberBuilder,
     MetadataBuilder;
 
 class KernelEnumBuilder extends SourceClassBuilder
@@ -136,7 +135,8 @@ class KernelEnumBuilder extends SourceClassBuilder
     KernelEnumBuilder enumBuilder = new KernelEnumBuilder.internal(metadata,
         name, members, types, cls, constants, toStringMap, intType, stringType,
         parent);
-    members.forEach((String name, MemberBuilder builder) {
+    // TODO(sigmund): dynamic should be `covariant MemberBuilder`.
+    members.forEach((String name, dynamic builder) {

[ahe, 2017/02/07 11:03:08]

I think I prefer this:

members.forEach((String name, dynamic b) {
  MemberBuilder builder = b;
...
}

Two or three other places. Thank you for adding the todo.

[Siggi Cherem (dart-lang), 2017/02/07 21:59:26]

Done. I had that in on my first change and I thought you wanted me to remove it
when switching to dynamic :), just added it back.

[ahe, 2017/02/08 19:59:23]

Yeah, sorry about that. Sometimes stuffs needs to be really concrete for me to
understand the trade offs. This is part of the reason I'd preferred to do this
task myself at a later time.

[Siggi Cherem (dart-lang), 2017/02/09 04:44:02]

No problem, I understand

       builder.parent = enumBuilder;
     });
     selfType.builder = enumBuilder;