Add the first very basic bits of a geofencing API.

Source/modules/geolocation/CircularRegion.idl

Index: Source/modules/geolocation/CircularRegion.idl
diff --git a/Source/modules/geolocation/CircularRegion.idl b/Source/modules/geolocation/CircularRegion.idl
new file mode 100644
index 0000000000000000000000000000000000000000..c4121e13ed840cfbc941438b75321cb870dce747
--- /dev/null
+++ b/Source/modules/geolocation/CircularRegion.idl
@@ -0,0 +1,17 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+[
+    RuntimeEnabled=Geofencing,
+    Exposed=Window&Worker,
+    GarbageCollected,
+    Constructor(Dictionary init)
+] interface CircularRegion : GeofencingRegion {
+    const double MIN_RADIUS = 1.0;
+    const double MAX_RADIUS = 100.0;
+
+    readonly attribute double latitude;
+    readonly attribute double longitude;
+    readonly attribute double radius;
+};