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

third_party/WebKit/Source/core/html/HTMLMediaElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
index 26c96f482d36418c0f2e33185ac42c97bb136068..9abaa3bce51d609685a59abedc3107565bde131f 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
@@ -284,6 +284,11 @@ String preloadTypeToString(WebMediaPlayer::Preload preloadType) {
   return String();
 }
 
+bool hasAudioVideoTracks() {

[chcunningham, 2016/11/29 22:39:18]

You can make this a media:: namespaced utilitiy method. See
https://cs.chromium.org/chromium/src/media/base/media.h

[mlamouri (slow - plz ping), 2016/11/30 09:34:00]

That wouldn't be available from Blink. Or did you mean creating something
similar in Blink?

[whywhat, 2016/11/30 20:45:39]

I've put it into HTMLMediaElement as a public static method. Both MediaSource
and SourceBuffer already use HTMLMediaElement and depend on it supporting media
tracks so seems fair.

+  return RuntimeEnabledFeatures::audioVideoTracksEnabled() ||
+         RuntimeEnabledFeatures::backgroundVideoTrackOptimizationEnabled();
+}

[mlamouri (slow - plz ping), 2016/11/30 09:34:00]

nit: can you name the method hasAudioVideoTracksEnabled()? I think the name
might be very confusing otherwise.

[whywhat, 2016/11/30 20:45:39]

The meaning is not about the feature enabled but if the media element uses media
tracks for the default source (if the page is not using the tracks itself).

mediaTracksEnabledInternally it is :)

+
 }  // anonymous namespace
 
 class HTMLMediaElement::AutoplayHelperClientImpl
@@ -2565,7 +2570,7 @@ void HTMLMediaElement::audioTrackChanged(AudioTrack* track) {
   BLINK_MEDIA_LOG << "audioTrackChanged(" << (void*)this
                   << ") trackId= " << String(track->id())
                   << " enabled=" << boolString(track->enabled());
-  DCHECK(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+  DCHECK(hasAudioVideoTracks());
 
   audioTracks().scheduleChangeEvent();
 
@@ -2620,7 +2625,7 @@ void HTMLMediaElement::selectedVideoTrackChanged(VideoTrack* track) {
   BLINK_MEDIA_LOG << "selectedVideoTrackChanged(" << (void*)this
                   << ") selectedTrackId="
                   << (track->selected() ? String(track->id()) : "none");
-  DCHECK(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+  DCHECK(hasAudioVideoTracks());
 
   if (track->selected())
     videoTracks().trackSelected(track->id());
@@ -3860,29 +3865,27 @@ DEFINE_TRACE_WRAPPERS(HTMLMediaElement) {
 }
 
 void HTMLMediaElement::createPlaceholderTracksIfNecessary() {
-  if (!RuntimeEnabledFeatures::audioVideoTracksEnabled() &&
-      !RuntimeEnabledFeatures::backgroundVideoTrackOptimizationEnabled()) {
+  if (!hasAudioVideoTracks())
     return;
-  }
 
   // Create a placeholder audio track if the player says it has audio but it
   // didn't explicitly announce the tracks.
-  if (hasAudio() && !audioTracks().length())
+  if (hasAudio() && !audioTracks().length()) {
     addAudioTrack("audio", WebMediaPlayerClient::AudioTrackKindMain,
-                  "Audio Track", "", true);
+                  "Audio Track", "", false);
+  }
 
   // Create a placeholder video track if the player says it has video but it
   // didn't explicitly announce the tracks.
-  if (hasVideo() && !videoTracks().length())
+  if (hasVideo() && !videoTracks().length()) {
     addVideoTrack("video", WebMediaPlayerClient::VideoTrackKindMain,
-                  "Video Track", "", true);
+                  "Video Track", "", false);
+  }
 }
 
 void HTMLMediaElement::selectInitialTracksIfNecessary() {
-  if (!RuntimeEnabledFeatures::audioVideoTracksEnabled() &&
-      !RuntimeEnabledFeatures::backgroundVideoTrackOptimizationEnabled()) {
+  if (!hasAudioVideoTracks())
     return;
-  }
 
   // Enable the first audio track if an audio track hasn't been enabled yet.
   if (audioTracks().length() > 0 && !audioTracks().hasEnabledTrack())