Implement MediaStreamTrack.getConstraints

third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.idl

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 19 matching lines @@
     readonly attribute DOMString id;
     readonly attribute DOMString label;
     attribute boolean enabled;
     readonly attribute boolean muted;
     readonly attribute boolean remote;
     readonly attribute DOMString readyState;
 
     [CallWith=ExecutionContext, RaisesException, DeprecateAs=MediaStreamTrackGetSources] static void getSources(MediaStreamTrackSourcesCallback callback);
     [ImplementedAs=stopTrack, RaisesException] void stop();
     [CallWith=ExecutionContext] MediaStreamTrack clone();
-
+    [RuntimeEnabled=MediaConstraints] MediaTrackConstraints getConstraints();

[Peter Beverloo, 2016/04/21 14:11:46]

More of a spec issue, but by returning a dictionary here the following equation
would return false:

  let track = ...;  // MediaStreamTrack instance
  track.getConstraints() === track.getConstraints()

A more modern version of doing this is by applying FrozenArray<>, which is being
introduced in crbug.com/515920. `constraints` can then just be a property and
equality would work as expected.

[hta - Chromium, 2016/04/24 09:58:26]

FrozenArray<> isn't a name/value map, though, and can't be used to contain a
dictionary (I think - haraken insists that dictionary types don't survive a
single cycle). I've grown to dislike dictionaries for many reasons, but they do
convert very nicely into Javascript objects.

     attribute EventHandler onmute;
     attribute EventHandler onunmute;
     attribute EventHandler onended;
 };
-