Implement autoplay gesture override experiment.

Source/web/WebSettingsImpl.cpp

 /*
  * Copyright (C) 2009 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 561 matching lines @@
 void WebSettingsImpl::setHyperlinkAuditingEnabled(bool enabled)
 {
     m_settings->setHyperlinkAuditingEnabled(enabled);
 }
 
 void WebSettingsImpl::setAsynchronousSpellCheckingEnabled(bool enabled)
 {
     m_settings->setAsynchronousSpellCheckingEnabled(enabled);
 }
 
+void WebSettingsImpl::setAutoplayExperimentMode(const WebString& mode)
+{
+    m_settings->setAutoplayExperimentMode(mode);
+}
+
 void WebSettingsImpl::setUnifiedTextCheckerEnabled(bool enabled)
 {
     m_settings->setUnifiedTextCheckerEnabled(enabled);
 }
 
 void WebSettingsImpl::setCaretBrowsingEnabled(bool enabled)
 {
     m_settings->setCaretBrowsingEnabled(enabled);
 }
 
@@ skipping 222 matching lines @@
 {
     m_devToolsEmulator->setUseMobileViewportStyle(enabled);
 }
 
 void WebSettingsImpl::setHidePinchScrollbarsNearMinScale(bool enabled)
 {
     m_devToolsEmulator->setHidePinchScrollbarsNearMinScale(enabled);
 }
 
 } // namespace blink