Add the first very basic bits of a geofencing API.

Source/modules/geolocation/GeofencingRegion.idl

Index: Source/modules/geolocation/GeofencingRegion.idl
diff --git a/Source/modules/gamepad/GamepadButton.idl b/Source/modules/geolocation/GeofencingRegion.idl
similarity index 67%
copy from Source/modules/gamepad/GamepadButton.idl
copy to Source/modules/geolocation/GeofencingRegion.idl
index 19d88ce77cdc808153c4250e1203526586640e01..4e22058d98b22fb2f0a7d196263ea4b9a458feab 100644
--- a/Source/modules/gamepad/GamepadButton.idl
+++ b/Source/modules/geolocation/GeofencingRegion.idl
@@ -3,9 +3,9 @@
 // found in the LICENSE file.
 
 [
+    RuntimeEnabled=Geofencing,
     NoInterfaceObject,
     GarbageCollected,
-] interface GamepadButton {
-    readonly attribute boolean pressed;
-    readonly attribute double value;
+] interface GeofencingRegion {
+    readonly attribute DOMString id;
 };