Reland r24563 and r24564 with fixes cumbersome API leading to leaks.

runtime/lib/object.cc

Index: runtime/lib/object.cc
===================================================================
--- runtime/lib/object.cc	(revision 24817)
+++ runtime/lib/object.cc	(working copy)
@@ -5,6 +5,7 @@
 #include "vm/bootstrap_natives.h"
 
 #include "vm/exceptions.h"
+#include "vm/heap.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
 #include "vm/stack_frame.h"
@@ -21,6 +22,22 @@
 }
 
 
+DEFINE_NATIVE_ENTRY(Object_getHash, 1) {
+  const Instance& instance = Instance::CheckedHandle(arguments->NativeArgAt(0));
+  Heap* heap = isolate->heap();
+  return Smi::New(heap->GetHash(instance.raw()));
+}
+
+
+DEFINE_NATIVE_ENTRY(Object_setHash, 2) {
+  const Instance& instance = Instance::CheckedHandle(arguments->NativeArgAt(0));
+  GET_NON_NULL_NATIVE_ARGUMENT(Smi, hash, arguments->NativeArgAt(1));
+  Heap* heap = isolate->heap();
+  heap->SetHash(instance.raw(), hash.Value());
+  return Object::null();
+}
+
+
 DEFINE_NATIVE_ENTRY(Object_toString, 1) {
   const Instance& instance = Instance::CheckedHandle(arguments->NativeArgAt(0));
   const char* c_str = instance.ToCString();