Rewrite mixin application handling in Fasta.

pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect

Index: pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect
diff --git a/pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect b/pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect
index ac14e5bda757338c816426c2f26f2695dec03e11..585c3d5e0bb2cda4715f7cf5bff084cd26d13b62 100644
--- a/pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect
+++ b/pkg/front_end/testcases/rasta/issue_000080.dart.outline.expect
@@ -9,6 +9,8 @@ class Mixin extends core::Object {
   method foo() → dynamic
     ;
 }
+abstract class Object&Mixin = core::Object with self::Mixin {
+}
 class Foo extends self::Object&Mixin {
   constructor •() → void
     ;
@@ -17,7 +19,5 @@ class Foo extends self::Object&Mixin {
   method bar() → dynamic
     ;
 }
-abstract class Object&Mixin = core::Object with self::Mixin {
-}
 static method main() → dynamic
   ;