Re-apply "Implement operator== and hashCode for bound closures."

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/js_backend/backend.dart	(revision 23383)
+++ sdk/lib/_internal/compiler/implementation/js_backend/backend.dart	(working copy)
@@ -1100,6 +1100,8 @@
             compiler.findHelper(const SourceString('iae')));
       } else if (cls == compiler.functionClass) {
         enqueuer.registerInstantiatedClass(compiler.closureClass, elements);
+        enqueuer.registerInstantiatedClass(
+            compiler.boundClosureClass, elements);
       } else if (cls == compiler.mapClass) {
         // The backend will use a literal list to initialize the entries
         // of the map.