Sped up hashCode by removing megamorphic call to _identityHashCode.

runtime/lib/object_patch.dart

Index: runtime/lib/object_patch.dart
diff --git a/runtime/lib/object_patch.dart b/runtime/lib/object_patch.dart
index 69723b38039f46b3eec4b1f5770768a6eea5b6eb..719e59220b6e268e084a99d43476689434167ba9 100644
--- a/runtime/lib/object_patch.dart
+++ b/runtime/lib/object_patch.dart
@@ -58,6 +58,11 @@ patch class Object {
   bool _instanceOf(instantiator_type_arguments, type, bool negate)
       native "Object_instanceOf";
 
+  // Group of functions for implementing fast simple instance of.
+  bool _simpleInstanceOf(type) native "Object_simpleInstanceOf";
+  bool _simpleInstanceOfTrue(type) => true;
+  bool _simpleInstanceOfFalse(type) => false;
+  
   bool _instanceOfDouble(bool negate) native "Object_instanceOfDouble";
   bool _instanceOfNum(bool negate) native "Object_instanceOfNum";
   bool _instanceOfInt(bool negate) native "Object_instanceOfInt";