Handle dynamic as bottom inside of function type reps

test/codegen/expect/cascade.js

Index: test/codegen/expect/cascade.js
diff --git a/test/codegen/expect/cascade.js b/test/codegen/expect/cascade.js
index 7791c0824ad3858dadca42c5eccec0c3f909bfcf..e44e19c311e5198faceb11dae67ed7489ab7b0f8 100644
--- a/test/codegen/expect/cascade.js
+++ b/test/codegen/expect/cascade.js
@@ -107,7 +107,7 @@ dart_library.library('cascade', null, /* Imports */[
     }
   }
   dart.setSignature(Foo, {
-    methods: () => ({test_final_field_generic: [dart.void, [core.Object]]})
+    methods: () => ({test_final_field_generic: [dart.void, [dart.dynamic]]})
   });
   // Exports:
   exports.A = A;