Add the Presentation API module and a single event target

Source/modules/presentation/Presentation.idl

 // 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.
 
+// http://webscreens.github.io/presentation-api/#presentation-interface
+
 [
-    NoInterfaceObject,
     GarbageCollected,
-] interface GamepadButton {
-    readonly attribute boolean pressed;
-    readonly attribute double value;
+    RuntimeEnabled=Presentation
+] interface Presentation : EventTarget {
+    attribute EventHandler onavailablechange;
 };