Autoplay: use an autoplay policy setting in Blink.

third_party/WebKit/public/web/WebSettings.h

 /*
  * 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 95 matching lines @@
   };
 
   // Defines the default for 'passive' field used in the AddEventListenerOptions
   // interface when javascript calls addEventListener.
   enum class PassiveEventListenerDefault {
     kFalse,        // Default of false.
     kTrue,         // Default of true.
     kForceAllTrue  // Force all values to be true even when specified.
   };
 
+  // Defines the autoplay policy to be used. Should match the enum class in
+  // web_preferences.h

[dcheng, 2017/04/27 15:57:17]

Is this in another CL? Or is this referencing AutoplayPolicy::Type?

+  enum class AutoplayPolicy {
+    kNoUserGestureRequired = 0,
+    kCrossOriginUserGestureRequired,

[dcheng, 2017/04/27 15:57:17]

FWIW, I find this name a bit confusing: to me, it reads "cross-origin user
gesture", where cross-origin is modifying user gesture, rather than "autoplay in
cross-origin subframe requires user gesture". *shrug*

kUserGestureRequiredForCrossOriginSubframe might be clearer, though it's also
more verbose.

+    kUserGestureRequired,
+  };
+
   // Sets value of a setting by its string identifier from Settings.in and
   // string representation of value. An enum's string representation is the
   // string representation of the integer value of the enum.
   virtual void SetFromStrings(const WebString& name,
                               const WebString& value) = 0;
 
   virtual bool ShrinksViewportContentToFit() const = 0;
   virtual bool ViewportEnabled() const = 0;
   virtual void SetAccelerated2dCanvasMSAASampleCount(int) = 0;
   virtual void SetAcceleratedCompositingEnabled(bool) = 0;
@@ skipping 12 matching lines @@
   // If set to true, allows frames with an https origin to run active
   // contents at an insecure URL. This includes WebSockets. Otherwise,
   // disallows it. The LocalFrameClient set to the frame may override the
   // value set by this method.
   virtual void SetAllowRunningOfInsecureContent(bool) = 0;
   virtual void SetAllowScriptsToCloseWindows(bool) = 0;
   virtual void SetAllowUniversalAccessFromFileURLs(bool) = 0;
   virtual void SetAlwaysShowContextMenuOnTouch(bool) = 0;
   virtual void SetAntialiased2dCanvasEnabled(bool) = 0;
   virtual void SetAntialiasedClips2dCanvasEnabled(bool) = 0;
+  virtual void SetAutoplayPolicy(AutoplayPolicy) = 0;
   virtual void SetAutoZoomFocusedNodeToLegibleScale(bool) = 0;
   virtual void SetBrowserSideNavigationEnabled(bool) = 0;
   virtual void SetClobberUserAgentInitialScaleQuirk(bool) = 0;
   virtual void SetCookieEnabled(bool) = 0;
-  virtual void SetCrossOriginMediaPlaybackRequiresUserGesture(bool) = 0;
   virtual void SetNavigateOnDragDrop(bool) = 0;
   virtual void SetCursiveFontFamily(const WebString&,
                                     UScriptCode = USCRIPT_COMMON) = 0;
   virtual void SetDNSPrefetchingEnabled(bool) = 0;
   virtual void SetDataSaverEnabled(bool) = 0;
   virtual void SetDOMPasteAllowed(bool) = 0;
   virtual void SetDefaultFixedFontSize(int) = 0;
   virtual void SetDefaultFontSize(int) = 0;
   virtual void SetDefaultTextEncodingName(const WebString&) = 0;
   virtual void SetDefaultVideoPosterURL(const WebString&) = 0;
@@ skipping 27 matching lines @@
   virtual void SetJavaScriptCanOpenWindowsAutomatically(bool) = 0;
   virtual void SetJavaScriptEnabled(bool) = 0;
   virtual void SetLoadsImagesAutomatically(bool) = 0;
   virtual void SetLoadWithOverviewMode(bool) = 0;
   virtual void SetShouldReuseGlobalForUnownedMainFrame(bool) = 0;
   virtual void SetProgressBarCompletion(ProgressBarCompletion) = 0;
   virtual void SetLocalStorageEnabled(bool) = 0;
   virtual void SetMainFrameClipsContent(bool) = 0;
   virtual void SetMainFrameResizesAreOrientationChanges(bool) = 0;
   virtual void SetMaxTouchPoints(int) = 0;
-  virtual void SetMediaPlaybackRequiresUserGesture(bool) = 0;
   virtual void SetMediaPlaybackGestureWhitelistScope(const WebString&) = 0;
   virtual void SetPresentationRequiresUserGesture(bool) = 0;
   virtual void SetEmbeddedMediaExperienceEnabled(bool) = 0;
   virtual void SetMinimumAccelerated2dCanvasSize(int) = 0;
   virtual void SetMinimumFontSize(int) = 0;
   virtual void SetMinimumLogicalFontSize(int) = 0;
   virtual void SetMockScrollbarsEnabled(bool) = 0;
   virtual void SetHideScrollbars(bool) = 0;
   virtual void SetOfflineWebApplicationCacheEnabled(bool) = 0;
   virtual void SetPassiveEventListenerDefault(PassiveEventListenerDefault) = 0;
@@ skipping 86 matching lines @@
   virtual void SetMediaControlsEnabled(bool) = 0;
   virtual void SetDoNotUpdateSelectionOnMutatingSelectionRange(bool) = 0;
 
  protected:
   ~WebSettings() {}
 };
 
 }  // namespace blink
 
 #endif