Store Object.observe state per-isolate rather than per-context

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index b0a6b5e81427e1588a89f1c269a2b1e90c78f98b..bfe9cc905904f9b50cb675d47dfcae333d6fd9ae 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -13222,6 +13222,12 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_HaveSameMap) {
   return isolate->heap()->ToBoolean(obj1->map() == obj2->map());
 }
 
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_GetObjectObservationState) {
+  ASSERT(args.length() == 0);
+  return isolate->heap()->object_observation_state();
+}
+
 // ----------------------------------------------------------------------------
 // Implementation of Runtime