Initial implementation of AudioTrack, AudioTrackList, VideoTrack, and VideoTrackList.

Source/core/html/track/AudioTrack.cpp

+// 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.
+
+#include "config.h"
+#include "core/html/track/AudioTrack.h"
+
+#include "core/html/HTMLMediaElement.h"
+#include "core/html/track/AudioTrackList.h"
+
+namespace WebCore {
+
+AudioTrack::AudioTrack(HTMLMediaElement* mediaElement, const AtomicString& id, const AtomicString& kind, const AtomicString& label, const AtomicString& language)
+    : TrackBase(TrackBase::AudioTrack, label, language, id)
+    , m_enabled(false)

[philipj_slow, 2014/03/09 09:04:14]

If I turn out to be right about
https://www.w3.org/Bugs/Public/show_bug.cgi?id=24977 then enabled should become
part of the argument list instead.

+{
+    ASSERT(mediaElement);

[philipj_slow, 2014/03/09 09:04:14]

Make it a reference instead? That TrackBase has it as a pointer can be an
internal detail.

[acolwell GONE FROM CHROMIUM, 2014/03/18 22:02:15]

No. Tracks can outlive the HTMLMediaElement if JS holds a reference to one.

[philipj_slow, 2014/03/20 16:17:39]

Ah, yes.

+    ASSERT(!id.isEmpty());
+
+    ScriptWrappable::init(this);
+    setKind(kind);
+    setMediaElement(mediaElement);
+}
+
+AudioTrack::~AudioTrack()
+{
+}
+
+void AudioTrack::setEnabled(bool enabled)
+{
+    if (enabled == m_enabled)
+        return;
+
+    m_enabled = enabled;
+
+    if (mediaElement())
+        mediaElement()->audioTrackChanged(id(), m_enabled);
+}
+
+const AtomicString& AudioTrack::alternativeKeyword()
+{
+    DEFINE_STATIC_LOCAL(const AtomicString, keyword, ("alternative", AtomicString::ConstructFromLiteral));
+    return keyword;
+}
+
+const AtomicString& AudioTrack::descriptionsKeyword()
+{
+    DEFINE_STATIC_LOCAL(const AtomicString, keyword, ("descriptions", AtomicString::ConstructFromLiteral));
+    return keyword;
+}
+
+const AtomicString& AudioTrack::mainKeyword()
+{
+    DEFINE_STATIC_LOCAL(const AtomicString, keyword, ("main", AtomicString::ConstructFromLiteral));
+    return keyword;
+}
+
+const AtomicString& AudioTrack::mainDescriptionsKeyword()
+{
+    DEFINE_STATIC_LOCAL(const AtomicString, keyword, ("main-desc", AtomicString::ConstructFromLiteral));
+    return keyword;
+}
+
+const AtomicString& AudioTrack::translationKeyword()
+{
+    DEFINE_STATIC_LOCAL(const AtomicString, keyword, ("translation", AtomicString::ConstructFromLiteral));
+    return keyword;
+}
+
+const AtomicString& AudioTrack::commentaryKeyword()
+{
+    DEFINE_STATIC_LOCAL(const AtomicString, keyword, ("commentary", AtomicString::ConstructFromLiteral));
+    return keyword;
+}
+
+bool AudioTrack::isValidKind(const AtomicString& kind) const

[philipj_slow, 2014/03/09 09:04:14]

I don't understand why this TrackBase::isValidKind is needed. TextTrack has
TextTrackKind so the bindings guarantee it's valid, and AudioTrack/VideoTrack
can currently only be created by us, so we can just assert that it's valid,
right?

[acolwell GONE FROM CHROMIUM, 2014/03/18 22:02:15]

I could probably move this functionality to TextTrack instead. For out-of-band
tracks kind can be set to invalid values. I think that is what this code was
trying to protect against. I'll refactor the TextTrack code so we just defend
the border where invalid values can enter the system and remove it from
TrackBase.

[philipj_slow, 2014/03/20 16:17:39]

Sounds like a plan. Even for out-of-band tracks we could just require the
backends to use a valid type, but I suppose it's a convenience to let them not
worry about it.

+{
+    return (kind == alternativeKeyword())
+        || (kind == descriptionsKeyword())
+        || (kind == mainKeyword())
+        || (kind == mainDescriptionsKeyword())
+        || (kind == translationKeyword())
+        || (kind == commentaryKeyword());
+}
+
+AtomicString AudioTrack::defaultKind() const
+{
+    return emptyAtom;
+}
+
+}