Don't try to set transparency on pixbufs that don't have any transparency....

chrome/browser/gtk/nine_box.cc

Index: chrome/browser/gtk/nine_box.cc
===================================================================
--- chrome/browser/gtk/nine_box.cc	(revision 20666)
+++ chrome/browser/gtk/nine_box.cc	(working copy)
@@ -138,11 +138,21 @@
     if (!pixbuf)
       continue;
 
+    if (!gdk_pixbuf_get_has_alpha(pixbuf))
+      continue;
+
     guchar* pixels = gdk_pixbuf_get_pixels(pixbuf);
     int rowstride = gdk_pixbuf_get_rowstride(pixbuf);
+    int width = gdk_pixbuf_get_width(pixbuf);
+    int height = gdk_pixbuf_get_height(pixbuf);
 
-    for (int i = 0; i < gdk_pixbuf_get_height(pixbuf); ++i) {
-      for (int j = 0; j < gdk_pixbuf_get_width(pixbuf); ++j) {
+    if (width * 4 > rowstride) {
+      NOTREACHED();
+      continue;
+    }
+
+    for (int i = 0; i < height; ++i) {
+      for (int j = 0; j < width; ++j) {
          guchar* pixel = &pixels[i * rowstride + j * 4];
          if (pixel[0] == 0xff && pixel[1] == 0xff && pixel[2] == 0xff) {
            pixel[3] = 0;