Autoplay: add document user activation flag in chrome://flags

content/renderer/render_view_impl.cc

 // Copyright (c) 2012 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 "content/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <memory>
 
@@ skipping 1017 matching lines @@
           WebSettings::AutoplayPolicy::kNoUserGestureRequired);
       break;
     case AutoplayPolicy::kUserGestureRequired:
       settings->SetAutoplayPolicy(
           WebSettings::AutoplayPolicy::kUserGestureRequired);
       break;
     case AutoplayPolicy::kUserGestureRequiredForCrossOrigin:
       settings->SetAutoplayPolicy(
           WebSettings::AutoplayPolicy::kUserGestureRequiredForCrossOrigin);
       break;
+    case AutoplayPolicy::kDocumentUserActivationRequired:
+      settings->SetAutoplayPolicy(
+          WebSettings::AutoplayPolicy::kDocumentUserActivationRequired);
+      break;
   }
 
   settings->SetViewportEnabled(prefs.viewport_enabled);
   settings->SetViewportMetaEnabled(prefs.viewport_meta_enabled);
   settings->SetShrinksViewportContentToFit(
       prefs.shrinks_viewport_contents_to_fit);
   settings->SetViewportStyle(
       static_cast<blink::WebViewportStyle>(prefs.viewport_style));
 
   settings->SetLoadWithOverviewMode(prefs.initialize_at_minimum_page_scale);
@@ skipping 1604 matching lines @@
                         input_event.GetCoalescedEventsPointers(), latency_info,
                         dispatch_type);
     return INPUT_EVENT_ACK_STATE_NOT_CONSUMED;
   }
   idle_user_detector_->ActivityDetected();
   return RenderWidget::HandleInputEvent(input_event, latency_info,
                                         dispatch_type);
 }
 
 }  // namespace content