Added Object._cid getter, optimized it. Added to (some) classes a static final _clCid. Use those to…

runtime/lib/object.cc

Index: runtime/lib/object.cc
===================================================================
--- runtime/lib/object.cc	(revision 22688)
+++ runtime/lib/object.cc	(working copy)
@@ -15,6 +15,13 @@
 DECLARE_FLAG(bool, enable_type_checks);
 
 
+DEFINE_NATIVE_ENTRY(Object_cid, 1) {
+  const Instance& instance = Instance::CheckedHandle(arguments->NativeArgAt(0));
+  const Class& cls = Class::Handle(instance.clazz());
+  return Smi::New(cls.id());
+}
+
+
 DEFINE_NATIVE_ENTRY(Object_toString, 1) {
   const Instance& instance = Instance::CheckedHandle(arguments->NativeArgAt(0));
   const char* c_str = instance.ToCString();