Work around bug where closures are missing #call to support delegation of #call to closures.

runtime/lib/mirrors_impl.dart

Index: runtime/lib/mirrors_impl.dart
diff --git a/runtime/lib/mirrors_impl.dart b/runtime/lib/mirrors_impl.dart
index f527df78f99fbf22317d7b165d9282c6bec723f3..86a19808a4cf3ded4296eac27e56fcdde7933e65 100644
--- a/runtime/lib/mirrors_impl.dart
+++ b/runtime/lib/mirrors_impl.dart
@@ -475,6 +475,15 @@ class _LocalClosureMirror extends _LocalInstanceMirror
     return _function;
   }
 
+  // TODO(12602): Remove this special case.
+  delegate(Invocation invocation) {
+    if (invocation.isMethod && (invocation.memberName == #call)) {
+      return this.apply(invocation.positionalArguments,
+                        invocation.namedArguments);
+    }
+    return super.delegate(invocation);
+  }
+
   InstanceMirror apply(List<Object> positionalArguments,
                        [Map<Symbol, Object> namedArguments]) {
     // TODO(12602): When closures get an ordinary call method, this can be