Disable background video track behind a feature flag

content/public/common/web_preferences.h

Index: content/public/common/web_preferences.h
diff --git a/content/public/common/web_preferences.h b/content/public/common/web_preferences.h
index 9702484f6eb0da70a52d612e79362f5821da64ad..dc38d29ee40c9a210a4119e20938cc4667ee0b59 100644
--- a/content/public/common/web_preferences.h
+++ b/content/public/common/web_preferences.h
@@ -262,6 +262,9 @@ struct CONTENT_EXPORT WebPreferences {
   // Whether download UI should be hidden on this page.
   bool hide_download_ui;
 
+  // If enabled, disabled video track when the video is in the background.
+  bool background_video_track_optimization_enabled;
+
   // We try to keep the default values the same as the default values in
   // chrome, except for the cases where it would require lots of extra work for
   // the embedder to use the same default value.