Pretend the video has no audio track if it is playing as part of autoplay muted.

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 97ece0f6a33a98bf679519fbd12e1112e291404f..e94419abf9a06c79c5d721e5d367b329e5b83cf6 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
@@ -2347,8 +2347,7 @@ void HTMLMediaElement::setMuted(bool muted) {
   if (m_muted == muted)
     return;
 
-  bool wasAutoplayingMuted =
-      !paused() && m_muted && isLockedPendingUserGesture();
+  bool wasAutoplayingMuted = isAutoplayingMuted();
   bool wasPendingAutoplayMuted = m_autoplayVisibilityObserver && paused() &&
                                  m_muted && isLockedPendingUserGesture();
 
@@ -2358,8 +2357,6 @@ void HTMLMediaElement::setMuted(bool muted) {
   m_muted = muted;
   m_autoplayHelper->mutedChanged();
 
-  updateVolume();
-
   scheduleEvent(EventTypeNames::volumechange);
 
   // If an element autoplayed while muted, it needs to be unlocked to unmute,
@@ -2375,6 +2372,10 @@ void HTMLMediaElement::setMuted(bool muted) {
     }
   }
 
+  // This is called after the volumechange event to make sure isAutoplayingMuted
+  // returns the right value when webMediaPlayer receives the volume update.
+  updateVolume();
+
   // If an element was a candidate for autoplay muted but not visible, it will
   // have a visibility observer ready to start its playback.
   if (wasPendingAutoplayMuted) {
@@ -3103,6 +3104,15 @@ void HTMLMediaElement::cancelledRemotePlaybackRequest() {
     remotePlaybackClient()->promptCancelled();
 }
 
+bool HTMLMediaElement::isAutoplayingMuted() {
+  if (!isHTMLVideoElement() ||
+      !RuntimeEnabledFeatures::autoplayMutedVideosEnabled()) {
+    return false;
+  }
+
+  return !paused() && muted() && isLockedPendingUserGesture();
+}
+
 void HTMLMediaElement::requestReload(const WebURL& newUrl) {
   DCHECK(webMediaPlayer());
   DCHECK(!m_srcObject);