[es6] Introduce a dedicated JSIteratorResult type.

src/hydrogen.h

Index: src/hydrogen.h
diff --git a/src/hydrogen.h b/src/hydrogen.h
index c5f35a32b6c8562bd1ecc7b62176127ea83bf0c3..e666d0a8bf81fe08b49be54936004d79b0a962b3 100644
--- a/src/hydrogen.h
+++ b/src/hydrogen.h
@@ -1358,6 +1358,9 @@ class HGraphBuilder {
                                               HValue* hash,
                                               LanguageMode language_mode);
 
+  // ES6 section 7.4.7 CreateIterResultObject ( value, done )
+  HValue* BuildCreateIterResultObject(HValue* value, HValue* done);
+
   HValue* BuildRegExpConstructResult(HValue* length,
                                      HValue* index,
                                      HValue* input);
@@ -2267,6 +2270,8 @@ class HOptimizedGraphBuilder : public HGraphBuilder, public AstVisitor {
   F(JSCollectionGetTable)              \
   F(StringGetRawHashField)             \
   F(TheHole)                           \
+  /* ES6 Iterators */                  \
+  F(CreateIterResultObject)            \
   /* Arrays */                         \
   F(HasFastPackedElements)             \
   F(GetPrototype)                      \