really fix gif movie registration



git-svn-id: http://skia.googlecode.com/svn/trunk@223 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/images/SkMovie_gif.cpp b/src/images/SkMovie_gif.cpp
index 68af85a..1138044 100644
--- a/src/images/SkMovie_gif.cpp
+++ b/src/images/SkMovie_gif.cpp
@@ -220,6 +220,8 @@
         if (memcmp(GIF_STAMP,   buf, GIF_STAMP_LEN) == 0 ||
                 memcmp(GIF87_STAMP, buf, GIF_STAMP_LEN) == 0 ||
                 memcmp(GIF89_STAMP, buf, GIF_STAMP_LEN) == 0) {
+            // must rewind here, since our construct wants to re-read the data
+            stream->rewind();
             return SkNEW_ARGS(SkGIFMovie, (stream));
         }
     }