Autoplay experiment: ignore viewport visibility requirements for audio.

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/html/AutoplayExperimentHelper.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLMediaElement.h"
 #include "core/layout/LayoutBox.h"
@@ skipping 479 matching lines @@
         return;
 
     m_recordedElement = true;
     recordAutoplayMetric(client().isHTMLVideoElement()
         ? AnyVideoElement
         : AnyAudioElement);
 }
 
 bool AutoplayExperimentHelper::requiresViewportVisibility() const
 {
-    return enabled(IfViewport) || enabled(IfPartialViewport);
+    return client().isHTMLVideoElement() && (enabled(IfViewport) || enabled(IfPartialViewport));
 }
 
 bool AutoplayExperimentHelper::isExperimentEnabled()
 {
     return m_mode != Mode::ExperimentOff;
 }
 
 } // namespace blink