Adding an experimental flag to block autoplay with sound in cross-origin iframes

third_party/WebKit/Source/core/frame/Settings.in

 # Defines properties which are available on the Settings object.
 #
 # Please think carefully before adding a new Setting.  Some questions to
 # consider are:
 # - Should this be a RuntimeEnabledFeature instead? Settings are for things
 #   which we support either values of at runtime.  Features are set at renderer
 #   process startup and are never changed. Features also tend to be set to a
 #   value based on the platform or the stability of the code in question, where
 #   as settings both codepaths need to be stable.
 # - How will you ensure test coverage of all relevant values of your setting?
@@ skipping 77 matching lines @@
 antialiased2dCanvasEnabled initial=true
 antialiasedClips2dCanvasEnabled initial=true
 accelerated2dCanvasMSAASampleCount type=int, initial=0
 
 hyperlinkAuditingEnabled initial=false
 allowRunningOfInsecureContent initial=true
 
 mediaControlsOverlayPlayButtonEnabled initial=false
 mediaPlaybackRequiresUserGesture initial=false
 
+# This flags overrides mediaPlaybackRequiresUserGesture
+crossOriginMediaPlaybackRequiresUserGesture initial=false
+
 presentationRequiresUserGesture initial=true
 
 scrollAnimatorEnabled initial=true
 
 # Used to disable threaded, compositor scrolling for testing purposes.
 # crbug.com/410974 tracks removal once alternative solutions for selective
 # main thread scrolling are supported.
 threadedScrollingEnabled initial=true, invalidate=Style
 
 # Used in layout tests for gesture tap highlights. Makes the highlights square
@@ skipping 317 matching lines @@
 
 # Whether download UI should be hidden for the current page content.
 hideDownloadUI initial=false
 
 # Whether or not to issue range requests for images and show placeholders.
 fetchImagePlaceholders initial=false
 
 # Whether the frame is a presentation receiver and should expose
 # `navigator.presentation.receiver`.
 presentationReceiver initial=false