Bug 1775442 - Remove selection from subtitles settings panel when fullscreen change. r=pip-reviewers,mhowell

Differential Revision: https://phabricator.services.mozilla.com/D150762

toolkit/components/pictureinpicture/content/player.js

@@ -342,6 +342,11 @@ let Player = {
             playerBottomControlsDOMRect: this.controlsBottom.getBoundingClientRect(),
           });
         }
+        // The subtitles settings panel gets selected when entering/exiting fullscreen even though
+        // user-select is set to none. I don't know why this happens or how to prevent so we just
+        // remove the selection when fullscreen is entered/exited.
+        let selection = window.getSelection();
+        selection.removeAllRanges();
         break;
       }