Fix bugs #16674 and #18112 with resizing TTY frames after switching terminals.

 lisp/window.el (window--pixel-to-total): Use FRAME's root window, not
 that of the selected frame.

lisp/ChangeLog

+2014-07-27  Eli Zaretskii  <eliz@gnu.org>
+
+	* window.el (window--pixel-to-total): Use FRAME's root window, not
+	that of the selected frame.  (Bug#18112, Bug#16674)
+
 2014-07-27  Andreas Schwab  <schwab@linux-m68k.org>
 	* textmodes/tex-mode.el (tex-font-lock-verb): Doc fix.

lisp/window.el

@@ -2230,7 +2230,7 @@ Optional argument HORIZONTAL non-nil means assign new total
 window widths from pixel widths."
   (setq frame (window-normalize-frame frame))
   (let* ((char-size (frame-char-size frame horizontal))
-	 (root (frame-root-window))
+	 (root (frame-root-window frame))
 	 (root-size (window-size root horizontal t))
 	 ;; We have to care about the minibuffer window only if it
 	 ;; appears together with the root window on this frame.