Introduce ES6 iterator for DOM objects.

Source/core/dom/Iterator.idl

Index: Source/core/dom/Iterator.idl
diff --git a/Source/modules/geofencing/GeofencingRegion.idl b/Source/core/dom/Iterator.idl
similarity index 66%
copy from Source/modules/geofencing/GeofencingRegion.idl
copy to Source/core/dom/Iterator.idl
index 4e22058d98b22fb2f0a7d196263ea4b9a458feab..87027c5bdac9d26ac0404df9ed40c057f021eb1b 100644
--- a/Source/modules/geofencing/GeofencingRegion.idl
+++ b/Source/core/dom/Iterator.idl
@@ -3,9 +3,9 @@
 // found in the LICENSE file.
 
 [
-    RuntimeEnabled=Geofencing,
-    NoInterfaceObject,
+    Iterable,
     GarbageCollected,
-] interface GeofencingRegion {
-    readonly attribute DOMString id;
+    NoInterfaceObject,
+] interface Iterator {
+    [CallWith=ScriptState, RaisesException] any next(optional any value);
 };