Returns true (1) if the renderer is currently in browser fullscreen. This
differs from window fullscreen in that browser fullscreen is entered using
the JavaScript Fullscreen API and modifies CSS attributes such as the
::backdrop pseudo-element and :fullscreen pseudo-structure. This function
can only be called on the UI thread.
Returns true (1) if the renderer is currently in browser fullscreen. This differs from window fullscreen in that browser fullscreen is entered using the JavaScript Fullscreen API and modifies CSS attributes such as the ::backdrop pseudo-element and :fullscreen pseudo-structure. This function can only be called on the UI thread.