Make rendering of MediaStreams reflect changes to its set of tracks.

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
@@ skipping 762 matching lines @@
 MediaError* HTMLMediaElement::error() const {
   return error_;
 }
 
 void HTMLMediaElement::SetSrc(const AtomicString& url) {
   setAttribute(srcAttr, url);
 }
 
 void HTMLMediaElement::SetSrcObject(MediaStreamDescriptor* src_object) {
   BLINK_MEDIA_LOG << "setSrcObject(" << (void*)this << ")";
+  if (src_object_ == src_object)

[foolip, 2017/07/05 08:49:44]

https://html.spec.whatwg.org/multipage/media.html#dom-media-srcobject says "On
setting, it must set the element's assigned media provider object to the new
value, and then invoke the element's media element load algorithm." with no
short-circuiting for when the value is the same. Is this a necessary part of the
fix?

[Guido Urdaneta, 2017/07/05 13:05:02]

Reverted the change and added a test to make sure the load algorithm runs when
reassigning the same object.

[foolip, 2017/07/05 13:13:52]

Great!

+    return;
+
   src_object_ = src_object;
   InvokeLoadAlgorithm();
 }
 
 HTMLMediaElement::NetworkState HTMLMediaElement::getNetworkState() const {
   return network_state_;
 }
 
 String HTMLMediaElement::canPlayType(const String& mime_type) const {
   MIMETypeRegistry::SupportsType support =
@@ skipping 3333 matching lines @@
       kMostlyFillViewportBecomeStableSeconds, BLINK_FROM_HERE);
 }
 
 void HTMLMediaElement::ViewportFillDebouncerTimerFired(TimerBase*) {
   mostly_filling_viewport_ = true;
   if (web_media_player_)
     web_media_player_->BecameDominantVisibleContent(mostly_filling_viewport_);
 }
 
 }  // namespace blink