Preliminary Harmony weak maps API implementation.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 34b7c2e229c457c7212514c3f1856094000c966d..9d850788aa8ca88e849db9db86b69a5153ddcd09 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -480,6 +480,12 @@ bool Object::IsJSFunctionProxy() {
 }
 
 
+bool Object::IsJSWeakMap() {
+  return Object::IsJSObject() &&
+      HeapObject::cast(this)->map()->instance_type() == JS_WEAKMAP_TYPE;
+}
+
+
 bool Object::IsJSContextExtensionObject() {
   return IsHeapObject()
       && (HeapObject::cast(this)->map()->instance_type() ==
@@ -2064,6 +2070,7 @@ CAST_ACCESSOR(JSArray)
 CAST_ACCESSOR(JSRegExp)
 CAST_ACCESSOR(JSProxy)
 CAST_ACCESSOR(JSFunctionProxy)
+CAST_ACCESSOR(JSWeakMap)
 CAST_ACCESSOR(Foreign)
 CAST_ACCESSOR(ByteArray)
 CAST_ACCESSOR(ExternalArray)
@@ -3794,6 +3801,9 @@ ACCESSORS(JSProxy, handler, Object, kHandlerOffset)
 ACCESSORS(JSProxy, padding, Object, kPaddingOffset)
 
 
+ACCESSORS(JSWeakMap, table, ObjectHashTable, kTableOffset)
+
+
 Address Foreign::address() {
   return AddressFrom<Address>(READ_INTPTR_FIELD(this, kAddressOffset));
 }