[Cocoa] Apply frameless masks before creating window, so fullscreen height works.
[Cocoa] Apply frameless masks before creating window, so fullscreen height works.

Doing it after leads to a titlebar height gap at the top of full-height
windows.

r0x0r/pywebview,r0x0r/pywebview,r0x0r/pywebview,r0x0r/pywebview,r0x0r/pywebview