Add map transition for observed objects

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index a4e70eb8ebda6b3d7dfbb944a21e11024dd4b2c1..bf04934605cad83b5fd5280233eac95d96196e47 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2333,6 +2333,10 @@ class JSObject: public JSReceiver {
   // ES5 Object.freeze
   MUST_USE_RESULT MaybeObject* Freeze(Isolate* isolate);
 
+
+  // Called the first time an object is observed with ES7 Object.observe.
+  MUST_USE_RESULT MaybeObject* SetObserved(Isolate* isolate);
+
   // Copy object
   MUST_USE_RESULT MaybeObject* DeepCopy(Isolate* isolate);
 
@@ -5477,8 +5481,10 @@ class Map: public HeapObject {
       int index,
       TransitionFlag flag);
   MUST_USE_RESULT MaybeObject* AsElementsKind(ElementsKind kind);
+
   MUST_USE_RESULT MaybeObject* CopyAsElementsKind(ElementsKind kind,
                                                   TransitionFlag flag);
+  MUST_USE_RESULT MaybeObject* CopyForObserved();
 
   MUST_USE_RESULT MaybeObject* CopyNormalized(PropertyNormalizationMode mode,
                                               NormalizedMapSharingMode sharing);