Media Capabilities: stub implementation of mediaCapabilities.query().

third_party/WebKit/Source/modules/mediacapabilities/MediaCapabilities.idl

+// Copyright 2017 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.
+
+// https://wicg.github.io/media-capabilities/#mediacapabilities
+
+[
+    Exposed=(Window, Worker),

[chcunningham, 2017/02/13 19:31:07]

MSE and EME have not been exposed to workers. There is some technical challenge
who's details I forget - perhaps the concern does not apply here (it probably
doesn't since we aren't really invoking the pipeline/decodeing etc...). +
wolenetz to remind me if this will be an issue

[wolenetz, 2017/02/13 22:33:24]

+mlamouri@ and ddorwin@ w.r.t. workers and HTMLMediaElement or EME.
There's a separate workers effort spinning up; I don't know yet if exposing your
API on worker is a potential problem or not.

[mlamouri (slow - plz ping), 2017/02/13 22:58:25]

This isn't implemented for workers. This only means that the interface is
exposed to the worker context but because WorkerNavigator doesn't expose an
object, it's useless. I will update this to remove the exposition.

+    RuntimeEnabled=MediaCapabilities
+] interface MediaCapabilities {
+    [CallWith=ScriptState] Promise<MediaDecodingAbility> query(MediaConfiguration configuration);
+};