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

content/child/runtime_features.cc

Index: content/child/runtime_features.cc
diff --git a/content/child/runtime_features.cc b/content/child/runtime_features.cc
index 7c1e8326c02641076e5638bf33394b0fea9f5e2d..9ded7576ef42eaf18b5845f7cb6da4226e4a7f11 100644
--- a/content/child/runtime_features.cc
+++ b/content/child/runtime_features.cc
@@ -44,8 +44,12 @@ static void SetRuntimeFeatureDefaultsForPlatform() {
   WebRuntimeFeatures::enableAutoplayMutedVideos(true);
   // Android does not yet support SystemMonitor.
   WebRuntimeFeatures::enableOnDeviceChange(false);
-#else
+#else  // defined(OS_ANDROID)
   WebRuntimeFeatures::enableNavigatorContentUtils(true);
+  if (base::FeatureList::IsEnabled(
+          features::kCrossOriginMediaPlaybackRequiresUserGesture)) {
+    WebRuntimeFeatures::enableAutoplayMutedVideos(true);
+  }
 #endif  // defined(OS_ANDROID)
 
 #if defined(OS_ANDROID) || defined(USE_AURA)