bug#16594: 24.3.50; very slow redraw when resizing windows horizontally

[Darren Hoo]

emacs -q
(scroll-bar-mode 'nil)
C-x 3

then try to resize the windows using mouse several times and emacs
redisplay is so slow that you can notice the fringes besides the drag
handle is repainted from top to bottom frame by frame.

profiling shows `read-event' takes much of the time, is this the real
cause?

- command-execute                                                 207  98%
 - call-interactively                                             207  98%
  - mouse-drag-vertical-line                                      202  96%
   - mouse-drag-line                                              202  96%
    - eval                                                        202  96%
     - track-mouse                                                202  96%
      - funcall                                                   202  96%
       - #<compiled 0x40a712ed>                                   202  96%
        - read-event                                              184  87%
         - redisplay_internal (C function)                          1   0%
            eval                                                    1   0%
  + profiler-report                                                 5   2%
- ...                                                               2   0%
   Automatic GC                                                     2   0%
+ redisplay_internal (C function)                                   1   0%


In GNU Emacs 24.3.50.81 (x86_64-apple-darwin13.0.0, NS apple-appkit-1265.00)
 of 2014-01-29 on darren-rmbp
Repository revision: 116189 rudalics@gmx.at-20140128094537-ajntocd34vgsenh3
Configured using:
 `configure --with-ns'

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  tooltip-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
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
ESC [ ? 1 ; 2 c ESC x r e p o r t TAB RET

Recent messages:
("/Applications/Emacs.app/Contents/MacOS/Emacs")
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

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