Setup getter and setter elements.

dart/frog/leg/emitter.dart

Index: dart/frog/leg/emitter.dart
diff --git a/dart/frog/leg/emitter.dart b/dart/frog/leg/emitter.dart
index 81539e589086aec983f996e329eec08d6ebd96c7..9e41c810dd87225a7d53218de8dd7d419e2155a2 100644
--- a/dart/frog/leg/emitter.dart
+++ b/dart/frog/leg/emitter.dart
@@ -52,10 +52,9 @@ function(child, parent) {
         String name = namer.getBailoutName(member);
         buffer.add('$prototype.$name = $codeBlock;\n');
       }
-    } else {
+    } else if (member.kind === ElementKind.FIELD) {
       // TODO(ngeoffray): Have another class generate the code for the
       // fields.
-      assert(member.kind === ElementKind.FIELD);
       if (compiler.universe.invokedSetters.contains(member.name)) {
         String setterName = namer.setterName(member.name);
         buffer.add('$prototype.$setterName = function(v){\n' +
@@ -66,6 +65,9 @@ function(child, parent) {
         buffer.add('$prototype.$getterName = function(){\n' +
           '  return this.${namer.getName(member)};\n}\n');
       }
+    } else {
+      compiler.internalError('unexpected kind: "${member.kind}"',
+                             element: member);
     }
   }