Rewrite mixin application handling in Fasta.

pkg/front_end/lib/src/fasta/source/outline_builder.dart

Index: pkg/front_end/lib/src/fasta/source/outline_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/source/outline_builder.dart b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
index 930766550c686d0cfa255c90c987a93a45f2c304..4cffd0ea693c06ffa6e59b123ff41ac9d3a13935 100644
--- a/pkg/front_end/lib/src/fasta/source/outline_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
@@ -436,10 +436,6 @@ class OutlineBuilder extends UnhandledListener {
     List<TypeVariableBuilder> typeVariables = pop();
     int charOffset = pop();
     String name = pop();
-    if (typeVariables != null && mixinApplication is MixinApplicationBuilder) {
-      mixinApplication.typeVariables = typeVariables;
-      mixinApplication.subclassName = name;
-    }
     int modifiers = Modifier.validate(pop());
     List<MetadataBuilder> metadata = pop();
     library.addNamedMixinApplication(metadata, name, typeVariables, modifiers,