[Video] Add dummy video/audio tracks inactive to select them later.

third_party/WebKit/Source/modules/mediasource/SourceBuffer.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 83 matching lines @@
     stringBuilder.append(" [");
     stringBuilder.appendNumber(r.start);
     stringBuilder.append(';');
     stringBuilder.appendNumber(r.end);
     stringBuilder.append(']');
   }
   stringBuilder.append(" }");
   return stringBuilder.toString();
 }
 
+bool hasAudioVideoTracks() {
+  return RuntimeEnabledFeatures::audioVideoTracksEnabled() ||
+         RuntimeEnabledFeatures::backgroundVideoTrackOptimizationEnabled();
+}
+
 }  // namespace
 
 SourceBuffer* SourceBuffer::create(
     std::unique_ptr<WebSourceBuffer> webSourceBuffer,
     MediaSource* source,
     GenericEventQueue* asyncEventQueue) {
   SourceBuffer* sourceBuffer =
       new SourceBuffer(std::move(webSourceBuffer), source, asyncEventQueue);
   sourceBuffer->suspendIfNeeded();
   return sourceBuffer;
@@ skipping 148 matching lines @@
                                          "while the SourceBuffer's append "
                                          "state is 'PARSING_MEDIA_SEGMENT'.");
     return;
   }
 
   // 7. Update the attribute to new timestamp offset.
   m_timestampOffset = offset;
 }
 
 AudioTrackList& SourceBuffer::audioTracks() {
-  DCHECK(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+  DCHECK(hasAudioVideoTracks());
   return *m_audioTracks;
 }
 
 VideoTrackList& SourceBuffer::videoTracks() {
-  DCHECK(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+  DCHECK(hasAudioVideoTracks());
   return *m_videoTracks;
 }
 
 double SourceBuffer::appendWindowStart() const {
   return m_appendWindowStart;
 }
 
 void SourceBuffer::setAppendWindowStart(double start,
                                         ExceptionState& exceptionState) {
   BLINK_SBLOG << __func__ << " this=" << this << " start=" << start;
@@ skipping 274 matching lines @@
   if (isRemoved())
     return;
 
   BLINK_SBLOG << __func__ << " this=" << this;
   if (m_pendingRemoveStart != -1) {
     cancelRemove();
   } else {
     abortIfUpdating();
   }
 
-  if (RuntimeEnabledFeatures::audioVideoTracksEnabled()) {
+  if (hasAudioVideoTracks()) {
     DCHECK(m_source);
     if (m_source->mediaElement()->audioTracks().length() > 0 ||
         m_source->mediaElement()->videoTracks().length() > 0) {
       removeMediaTracks();
     }
   }
 
   m_webSourceBuffer->removedFromMediaSource();
   m_webSourceBuffer.reset();
   m_source = nullptr;
   m_asyncEventQueue = nullptr;
 }
 
 double SourceBuffer::highestPresentationTimestamp() {
   DCHECK(!isRemoved());
 
   double pts = m_webSourceBuffer->highestPresentationTimestamp();
   BLINK_SBLOG << __func__ << " this=" << this << ", pts=" << pts;
   return pts;
 }
 
 void SourceBuffer::removeMediaTracks() {
-  DCHECK(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+  DCHECK(hasAudioVideoTracks());
   // Spec:
   // http://w3c.github.io/media-source/#widl-MediaSource-removeSourceBuffer-void-SourceBuffer-sourceBuffer
   DCHECK(m_source);
 
   HTMLMediaElement* mediaElement = m_source->mediaElement();
   DCHECK(mediaElement);
   // 3. Let SourceBuffer audioTracks list equal the AudioTrackList object
   //    returned by sourceBuffer.audioTracks.
   // 4. If the SourceBuffer audioTracks list is not empty, then run the
   //    following steps:
@@ skipping 143 matching lines @@
   return trackDefault ? AtomicString(trackDefault->language()) : "";
 }
 
 bool SourceBuffer::initializationSegmentReceived(
     const WebVector<MediaTrackInfo>& newTracks) {
   BLINK_SBLOG << __func__ << " this=" << this << " tracks=" << newTracks.size();
   DCHECK(m_source);
   DCHECK(m_source->mediaElement());
   DCHECK(m_updating);
 
-  if (!RuntimeEnabledFeatures::audioVideoTracksEnabled()) {
+  if (!hasAudioVideoTracks()) {
     if (!m_firstInitializationSegmentReceived) {
       m_source->setSourceBufferActive(this, true);
       m_firstInitializationSegmentReceived = true;
     }
     return true;
   }
 
   // Implementation of Initialization Segment Received, see
   // https://w3c.github.io/media-source/#sourcebuffer-init-segment-received
 
@@ skipping 536 matching lines @@
   visitor->trace(m_asyncEventQueue);
   visitor->trace(m_appendBufferAsyncPartRunner);
   visitor->trace(m_removeAsyncPartRunner);
   visitor->trace(m_audioTracks);
   visitor->trace(m_videoTracks);
   EventTargetWithInlineData::trace(visitor);
   ActiveDOMObject::trace(visitor);
 }
 
 }  // namespace blink