bug#25845: 25.1; underline height moves

[ynyaaa@gmail.com]

Evaluating the form below, underline is displayed as one line at first.
Then move text cursor on Y, underline of Y moves down.
Then move text cursor on X and insert any text,
height of underline of Y moves back.

(insert (propertize "X" 'face '(:underline t))
        (propertize "Y" 'face '(:underline t :height 5.0)))




In GNU Emacs 25.1.1 (i686-w64-mingw32)
 of 2016-09-18 built on LAPHROAIG
Windowing system distributor 'Microsoft Corp.', version 6.0.6002
Configured using:
 'configure --host=i686-w64-mingw32 --without-dbus
 --without-compress-install CFLAGS=-static'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS

Important settings:
  value of $LANG: JPN
  locale-coding-system: cp932

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:

Load-path shadows:
None found.

Features:
(network-stream nsm starttls tls gnutls mailalias smtpmail auth-source
cl-seq eieio byte-opt bytecomp byte-compile cconv eieio-core cl-macs gv
cus-edit cus-start cus-load wid-edit debug cl-extra misearch
multi-isearch pp shadow sort mail-extr emacsbug message dired
format-spec rfc822 mml mml-sec password-cache epg epg-config gnus-util
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util help-fns
mail-prsvr mail-utils rect help-mode easymenu cl-loaddefs pcase cl-lib
time-date mule-util japan-util tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel dos-w32 ls-lisp disp-table
w32-win w32-vars term/common-win tool-bar dnd fontset image regexp-opt
fringe tabulated-list newcomment elisp-mode lisp-mode prog-mode register
page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core frame cl-generic cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese charscript case-table epa-hook
jka-cmpr-hook help simple abbrev minibuffer cl-preloaded nadvice
loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote w32notify w32 multi-tty
make-network-process emacs)

Memory information:
((conses 8 128272 20044)
 (symbols 32 22599 0)
 (miscs 32 108 321)
 (strings 16 23964 5016)
 (string-bytes 1 663671)
 (vectors 8 16199)
 (vector-slots 4 552710 15304)
 (floats 8 223 395)
 (intervals 28 1182 501)
 (buffers 520 26))