Add debug mirror support for ES6 Map/Set iterators.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 37e0ddc34d870acf1a45a87f0a4c76e6c95df198..d5433a6a269836955df2bd7f9a4c9380e53a1b7c 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -1626,6 +1626,18 @@ class V8_EXPORT Value : public Data {
   bool IsSet() const;
 
   /**
+   * Returns true if this value is a Map Iterator.
+   * This is an experimental feature.
+   */
+  bool IsMapIterator() const;
+
+  /**
+   * Returns true if this value is a Set Iterator.
+   * This is an experimental feature.
+   */
+  bool IsSetIterator() const;
+
+  /**
    * Returns true if this value is a WeakMap.
    * This is an experimental feature.
    */