emscripten CAP/NUM lock not in sync after a key is pressed

[qunying]

As describe in #5267, due to limitation of browser, we could not get the proper key state without a physical key press event involved.

Using the same test code in 5267, when Cap/Numlock states are changed outside of browser, bring focus back to browser, press a physical key, the Cap/Numlock state is not sync with keyboard.

While testing with browser with the enclosed html file, the key state is reported correctly.
focus.html.gz