Presentation API: implement .getAvalability() (Blink side).

Source/modules/presentation/PresentationAvailability.idl

Index: Source/modules/presentation/PresentationAvailability.idl
diff --git a/Source/modules/presentation/PresentationAvailability.idl b/Source/modules/presentation/PresentationAvailability.idl
new file mode 100644
index 0000000000000000000000000000000000000000..1aa8de6cfafcb24e834714c1d4928414daa6f5f1
--- /dev/null
+++ b/Source/modules/presentation/PresentationAvailability.idl
@@ -0,0 +1,15 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.

[whywhat, 2015/07/02 22:32:37]

nit: s/2014/2015

[mlamouri (slow - plz ping), 2015/07/03 13:58:26]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// https://w3c.github.io/presentation-api/

[whywhat, 2015/07/02 22:32:37]

nit: replace with https://w3c.github.io/presentation-api/#interface-availability

[mlamouri (slow - plz ping), 2015/07/03 13:58:26]

Done.

+
+[
+    ActiveDOMObject,
+    GarbageCollected,
+    RuntimeEnabled=Presentation,
+] interface PresentationAvailability : EventTarget {
+    readonly attribute boolean value;
+
+    attribute EventHandler onchange;
+};