Engine-rendered pages line up with other browsers more precisely

Four layout fixes that bring the pages you open with the Floati engine closer to what other browsers show, down to the pixel. Documentation sites and blogs that set aside room for a scrollbar now wrap their text at the same width instead of a little too wide; code samples written in a custom fixed-width font come out full-size again rather than about a fifth too small; a full-height app page now reports its real on-screen size to the code running on it; and every page ends exactly at its content, with no stray gap at the bottom.