[Android, Media] Don't unlock MediaStream elements; instead allow MS to autoplay without a gesture.

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

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple 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 1014 matching lines @@
 
     if (fastHasAttribute(mutedAttr))
         m_muted = true;
     updateVolume();
 
     DCHECK(!m_mediaSource);
 
     bool attemptLoad = true;
 
     bool isStreamOrBlobUrl = source.isMediaStream() || url.protocolIs(mediaSourceBlobProtocol);
     if (isStreamOrBlobUrl) {

[sof, 2016/06/27 15:10:47]

The logic looks a bit strange now - more readable as

  if (isStreamOrBlobUrl && !source.isMediaStream()) 

perhaps?

[whywhat, 2016/06/27 15:35:58]

Ok, I guess the overall condition triggering the code below comes down to

((source.isMediaStream() || url.protocolIs(mediaSourceBlobProtocol) &&
!source.isMediaStream() && (!source.isURL() ||
!isMediaStreamURL(url.getString()))

We could definitely remove source.isMediaStrem() from the first bracket:

url.protocolIs(mediaSourceBlobProtocol) && !source.isMediaStream() &&
(!source.isURL() || !isMediaStreamURL(url.getString()))

Maybe replace with:

isMediaStream = source.isMediaStream() || (source.isURL() &&
isMediaStreamURL(url.getString()));
isMediaSourceUrl = url.protocolIs(mediaSourceBlobProtocol) && !isMediaStream;
if (isMediaSourceUrl) {
  m_mediaSource = ...
  ...
}

WDYT?

Hm, isStreamOrBlobUrl is used elsewhere :(

Seems like "source.isURL() && isMediaStreamURL(url.getString())" is important
for m_mediaSource logic nested below but not for isStreamOrBlobUrl below? Does
it mean registered media stream URLs are ignored sometimes?

[sof, 2016/06/27 18:54:06]

That makes it a lot clearer, i.e., check if a media source blob: URL is for a
registered source. And try to use that media source, if so.

I'd just leave the isStreamOrBlobUrl as it is.
That question I'll leave to the grownups working with media element every day :)

[whywhat, 2016/06/27 19:00:50]

Not sure if it became much more clearer but I took a stab at it. Further
suggestions are welcome.

         bool isMediaStream = source.isMediaStream() || (source.isURL() && isMediaStreamURL(url.getString()));
-        if (isMediaStream) {
-            m_autoplayHelper->unlockUserGesture(GesturelessPlaybackEnabledByStream);
-        } else {
+        if (!isMediaStream) {
             m_mediaSource = HTMLMediaSource::lookup(url.getString());
 
             if (m_mediaSource) {
                 if (!m_mediaSource->attachToElement(this)) {
                     // Forget our reference to the MediaSource, so we leave it alone
                     // while processing remainder of load failure.
                     m_mediaSource = nullptr;
                     attemptLoad = false;
                 }
             }
@@ skipping 166 matching lines @@
     }
     DCHECK_EQ(m_deferredLoadState, WaitingForStopDelayingLoadEventTask);
     m_deferredLoadState = WaitingForTrigger;
 }
 
 WebMediaPlayer::LoadType HTMLMediaElement::loadType() const
 {
     if (m_mediaSource)
         return WebMediaPlayer::LoadTypeMediaSource;
 
-    if (m_srcObject || isMediaStreamURL(m_currentSrc.getString()))
+    if (m_srcObject || (!m_currentSrc.isNull() && isMediaStreamURL(m_currentSrc.getString())))
         return WebMediaPlayer::LoadTypeMediaStream;
 
     return WebMediaPlayer::LoadTypeURL;
 }
 
 bool HTMLMediaElement::textTracksAreReady() const
 {
     // 4.8.10.12.1 Text track model
     // ...
     // The text tracks of a media element are ready if all the text tracks whose mode was not
@@ skipping 2481 matching lines @@
 void HTMLMediaElement::unlockUserGesture()
 {
     m_lockedPendingUserGesture = false;
 }
 
 bool HTMLMediaElement::isGestureNeededForPlayback() const
 {
     if (!m_lockedPendingUserGesture)
         return false;
 
+    if (loadType() == WebMediaPlayer::LoadTypeMediaStream)
+        return false;
+
     // We want to allow muted video to autoplay if:
     // - the flag is enabled;
     // - Data Saver is not enabled;
     // - Autoplay is enabled in settings;
     if (isHTMLVideoElement()
         && muted()
         && RuntimeEnabledFeatures::autoplayMutedVideosEnabled()
         && !(document().settings() && document().settings()->dataSaverEnabled())
         && isAutoplayAllowedPerSettings()) {
         return false;
@@ skipping 285 matching lines @@
 
 IntRect HTMLMediaElement::AutoplayHelperClientImpl::absoluteBoundingBoxRect() const
 {
     IntRect result;
     if (LayoutObject* object = m_element->layoutObject())
         result = object->absoluteBoundingBoxRect();
     return result;
 }
 
 } // namespace blink