Make WINDOW fill its frame.
Only the frame WINDOW is on is affected. WINDOW must be a valid window
and defaults to the selected one.
Optional argument ROOT, if non-nil, must specify an internal window such
that WINDOW is in its window subtree. If this is the case, replace ROOT
by WINDOW and leave alone any windows not part of ROOT's subtree.
When WINDOW is live try to reduce display jumps by keeping the text
previously visible in WINDOW in the same place on the frame. Doing this
depends on the value of (window-start WINDOW), so if calling this
function in a program gives strange scrolling, make sure the
window-start value is reasonable when this function is called. (fn &optional WINDOW ROOT)