Enable user gesture requirement for autoplay experiment.

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 410 matching lines @@
 #if !ENABLE(OILPAN)
     , m_weakPtrFactory(this)
 #endif
 {
 #if ENABLE(OILPAN)
     ThreadState::current()->registerPreFinalizer(this);
 #endif
 
     WTF_LOG(Media, "HTMLMediaElement::HTMLMediaElement(%p)", this);
 
-    if (document.settings() && document.settings()->mediaPlaybackRequiresUserGesture())
+    // If any experiment is enabled, then we want to enable a user gesture by
+    // default, else the experiment does nothing.

[philipj_slow, 2016/04/05 11:17:51]

s/else/otherwise/

[liberato (no reviews please), 2016/04/25 22:38:44]

Done.

+    if ((document.settings() && document.settings()->mediaPlaybackRequiresUserGesture())

[philipj_slow, 2016/04/05 11:17:51]

Can't the same code that enables the experiment also set this setting?

[mlamouri (slow - plz ping), 2016/04/21 17:11:35]

They are fairly close:
https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/r...

[liberato (no reviews please), 2016/04/25 22:38:44]

in PS{2,3}, i've left it as-is to avoid parsing the experiment string.

if either of you feel strongly, please let me know and i'll move it.

[liberato (no reviews please), 2016/04/25 22:38:44]

the experiment is enabled by copying the string around, until it ends up in
blink::Settings::autoplayExperimentMode.  nothing attempts to interpret it;
that's all done in HTMLMediaElement.

that's why i just override in the element.  it keeps the interpretation of the
string centralized.

+        || m_autoplayHelper->isExperimentEnabled()) {
         m_userGestureRequiredForPlay = true;
+    }
 
     setHasCustomStyleCallbacks();
     addElementToDocumentMap(this, &document);
 
     UseCounter::count(document, UseCounter::HTMLMediaElement);
 }
 
 HTMLMediaElement::~HTMLMediaElement()
 {
     WTF_LOG(Media, "HTMLMediaElement::~HTMLMediaElement(%p)", this);
@@ skipping 3429 matching lines @@
 }
 
 #if !ENABLE(OILPAN)
 WeakPtr<HTMLMediaElement> HTMLMediaElement::createWeakPtr()
 {
     return m_weakPtrFactory.createWeakPtr();
 }
 #endif
 
 } // namespace blink