Synchronize with r15701.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index f4fc560b9795854f2e018a750bc656ae7c53c1b5..71df891cece97a3f4e14bbf703dd03c4120cb202 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1946,7 +1946,7 @@ class JSObject: public JSReceiver {
                              Handle<Object> setter,
                              PropertyAttributes attributes);
 
-  Object* LookupAccessor(Name* name, AccessorComponent component);
+  MaybeObject* LookupAccessor(Name* name, AccessorComponent component);
 
   MUST_USE_RESULT MaybeObject* DefineAccessor(AccessorInfo* info);
 
@@ -2335,6 +2335,10 @@ 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);
 
@@ -4675,10 +4679,6 @@ class Code: public HeapObject {
   // [to_boolean_foo]: For kind TO_BOOLEAN_IC tells what state the stub is in.
   inline byte to_boolean_state();
 
-  // [compare_nil]: For kind COMPARE_NIL_IC tells what state the stub is in.
-  byte compare_nil_state();
-  byte compare_nil_value();
-
   // [has_function_cache]: For kind STUB tells whether there is a function
   // cache is passed to the stub.
   inline bool has_function_cache();
@@ -5483,8 +5483,10 @@ 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);
@@ -5505,6 +5507,13 @@ class Map: public HeapObject {
   int NumberOfDescribedProperties(DescriptorFlag which = OWN_DESCRIPTORS,
                                   PropertyAttributes filter = NONE);
 
+  // Returns the number of slots allocated for the initial properties
+  // backing storage for instances of this map.
+  int InitialPropertiesLength() {
+    return pre_allocated_property_fields() + unused_property_fields() -
+        inobject_properties();
+  }
+
   // Casting.
   static inline Map* cast(Object* obj);