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

src/runtime.h

Index: src/runtime.h
diff --git a/src/runtime.h b/src/runtime.h
index c8029065f6908ce9f5d04c695dea00ffb098d687..848cdf99aed249df40b2e4a0801f7d055e791d51 100644
--- a/src/runtime.h
+++ b/src/runtime.h
@@ -317,6 +317,13 @@ namespace internal {
   F(WeakMapDelete, 2, 1) \
   F(WeakMapSet, 3, 1) \
   \
+  /* Object observation */ \
+  F(GetObjectObservationState, 0, 1) \
+  F(CreateObjectHashTable, 0, 1) \
+  F(ObjectHashTableGet, 2, 1) \
+  F(ObjectHashTableSet, 3, 1) \
+  F(ObjectHashTableHas, 2, 1) \
+  \
   /* Statements */ \
   F(NewClosure, 3, 1) \
   F(NewObject, 1, 1) \