bug#21714: 25.0.50; image-metadata using Emacs --with-ns prevents *.gif animation.

[Keith David Bershatsky]

When using Emacs built --with-ns on OSX 10.6.8, the function `image-metadata` 
returns `nil` when trying to animate a *.gif file with the built-in image-mode 
by pressing the return key.  I suspect it is because `valid_image_p` returns 
`nil`, but I do not know how to test that internal function.

When opening a *.gif image, Emacs successfully displays the first image in the 
series of multiple images.  Pressing the return key yields:  "No image 
animation."

OSX has its own built-in image support when building --with-ns, which is why I 
am able to see the first of the *.gif images.

(image-type-available-p 'gif) returns t, so I am fairly certain I have image 
support.

Animation works on Emacs for Windows, but not OSX.

Thanks,

Keith

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

In GNU Emacs 25.0.50.1 (x86_64-apple-darwin10.8.0, NS appkit-1038.36 Version 
10.6.8 (Build 10K549))
 of 2015-10-13
Repository revision: 6d6bf466477b004035a4314886e35214c6f8603b
Windowing system distributor 'Apple', version 10.3.1038
Configured using:
 'configure --with-ns --without-imagemagick --enable-checking=glyphs'

Configured features:
RSVG DBUS ACL LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
  locale-coding-system: utf-8-unix

Major mode: C

Minor modes in effect:
  tb-mode: t
  sb-mode: t
  ml-mode: t
  sd-mode: t
  fl-mode: t
  bc-mode: t
  +-mode: t
  buffer-read-only: t
  abbrev-mode: t

Recent messages:
Type C-c C-c to view the image as text.
Wrote /Users/HOME/.0.data/.0.emacs/.lock
Emacs:  image-metadata
*beep*
if: End of buffer

Load-path shadows:
None found.

Features:
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ps-print ps-def lpr epg-config enriched lawlist-w3m doc-view jka-compr
image-mode ccl lawlist-vl lawlist-view lawlist-undo lawlist-txt
lawlist-tm lawlist-tex compare-w lawlist-tabbar lawlist-speedbar
lawlist-shell info esh-groups ehelp ange-ftp lawlist-sgml lawlist-sb
lawlist-saveplace lawlist-ruler lawlist-replace lawlist-rectangle
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faces cus-face macroexp files text-properties overlay sha1 md5 base64
format env code-pages mule custom widget hashtable-print-readable
backquote dbusbind cocoa ns multi-tty make-network-process emacs)

Memory information:
((conses 16 2395843 198980)
 (symbols 48 89769 0)
 (miscs 40 1373 1067)
 (strings 32 212905 17549)
 (string-bytes 1 7685690)
 (vectors 16 44361)
 (vector-slots 8 1091868 14715)
 (floats 8 4334 755)
 (intervals 56 1101 110)
 (buffers 976 15))