Remove few more errors in mac scons build.

webkit/port/platform/image-decoders/gif/GIFImageReader.h

Index: webkit/port/platform/image-decoders/gif/GIFImageReader.h
===================================================================
--- webkit/port/platform/image-decoders/gif/GIFImageReader.h	(revision 6978)
+++ webkit/port/platform/image-decoders/gif/GIFImageReader.h	(working copy)
@@ -165,11 +165,11 @@
     int version;                /* Either 89 for GIF89 or 87 for GIF87 */
     unsigned screen_width;       /* Logical screen width & height */
     unsigned screen_height;
-    int global_colormap_size;   /* Size of global colormap array. */
-    int images_decoded;         /* Counts completed frames for animated GIFs */
-    int images_count;           /* Counted all frames seen so far (including incomplete frames) */
-    int loop_count;             /* Netscape specific extension block to control
-                                   the number of animation loops a GIF renders. */
+    int global_colormap_size;    /* Size of global colormap array. */
+    unsigned int images_decoded; /* Counts completed frames for animated GIFs */
+    int images_count;            /* Counted all frames seen so far (including incomplete frames) */
+    int loop_count;              /* Netscape specific extension block to control
+                                    the number of animation loops a GIF renders. */
     
     // Not really global, but convenient to locate here.
     int count;                  /* Remaining # bytes in sub-block */