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..15b0b3ee6c79fb8791ee454ef03f571313acf5ae 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_WEAK_MAP_TYPE;
+}
+
+
 bool Object::IsJSContextExtensionObject() {
   return IsHeapObject()
       && (HeapObject::cast(this)->map()->instance_type() ==
@@ -1414,6 +1420,8 @@ int JSObject::GetHeaderSize() {
       return JSValue::kSize;
     case JS_ARRAY_TYPE:
       return JSValue::kSize;
+    case JS_WEAK_MAP_TYPE:
+      return JSWeakMap::kSize;
     case JS_REGEXP_TYPE:
       return JSValue::kSize;
     case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
@@ -2064,6 +2072,7 @@ 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 +3803,9 @@ 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));
 }