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

chrome/browser/gtk/nine_box.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/gtk/nine_box.h"
 
 #include "app/resource_bundle.h"
 #include "app/theme_provider.h"
 #include "base/basictypes.h"
 #include "base/gfx/gtk_util.h"
@@ skipping 120 matching lines @@
   const int height = gdk_pixbuf_get_height(images_[1]);
   TileImage(cr, images_[1], x, y, width, height);
 }
 
 void NineBox::ChangeWhiteToTransparent() {
   for (int image_idx = 0; image_idx < 9; ++image_idx) {
     GdkPixbuf* pixbuf = images_[image_idx];
     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;
          }
       }
     }
   }
 }
 
 void NineBox::ContourWidget(GtkWidget* widget) const {
@@ skipping 30 matching lines @@
     NOTREACHED();
     return;
   }
 
   // Reload images.
   for (size_t i = 0; i < arraysize(image_ids_); ++i) {
     images_[i] = image_ids_[i] ?
                  theme_provider_->GetPixbufNamed(image_ids_[i]) : NULL;
   }
 }