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 8df90d2887cffb3d87fecc38446aeb68c33bf63e..1303b50686db08adfed22185d40e0918cb70c127 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -1614,6 +1614,18 @@ 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.
    */