Need to wait another frame for spatnav.

As part of trying to remove the forced UpdateStyleAndLayoutTree on
parsing finished, this test started failing. Parsing the document would
finish and force a style update after display is set to none, but before
the promise is resolved through rAF. Add another rAF to allow for a
lifecycle update of the computed style instead.

Bug: 742413
Change-Id: I91d21b5cd871d82d81dd8fb156465762ad594318
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1627355Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662599}

third_party/blink/web_tests/virtual/focusless-spat-nav/fast/spatial-navigation/focusless/snav-focusless-display-none-editable.html

@@ -31,7 +31,7 @@
       second.style.display = "none";
       // Need a rAF for automated testing since focus won't be reevaluated
       // until BeginFrame.
-      requestAnimationFrame(resolve);
+      requestAnimationFrame(() => requestAnimationFrame(resolve));
     });
   }