testsuite: Fix broken test

The test was referencing a nonexisting image.

Plus, node parsing cannot reference relative URLs.

testsuite/gsk/compare/scaled-texture.node

@@ -1,6 +1,17 @@
 container {
   texture-scale {
-    texture: url("some-10x10-image-with-content.png");
+    texture: url("data:image/png;base64,\
+iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAABhWlDQ1BJQ0MgcHJvZmlsZQAAKJF9\
+kT1Iw1AUhU9TpSIVBztIUchQxcEuKuKoVShChVArtOpg8tI/aNKQpLg4Cq4FB38Wqw4uzro6uAqC\
+4A+Iq4uToouUeF9SaBHjhcf7OO+ew3v3AUKjwjSraxbQdNtMJxNiNrcqhl4RxDACGENUZpYxJ0kp\
++NbXPXVS3cV5ln/fn9Wn5i0GBETiWWaYNvEG8fSmbXDeJ46wkqwSnxOPm3RB4keuKx6/cS66LPDM\
+iJlJzxNHiMViBysdzEqmRjxFHFM1nfKFrMcq5y3OWqXGWvfkLwzn9ZVlrtMaQhKLWIIEEQpqKKMC\
+G3HadVIspOk84eOPun6JXAq5ymDkWEAVGmTXD/4Hv2drFSYnvKRwAuh+cZyPESC0CzTrjvN97DjN\
+EyD4DFzpbX+1Acx8kl5va7EjoH8buLhua8oecLkDDD4Zsim7UpCWUCgA72f0TTlg4BboXfPm1jrH\
+6QOQoVmlboCDQ2C0SNnrPu/u6Zzbvz2t+f0AkpVys4Vzl18AAAAGYktHRABmAGYAZge6Sm0AAAAJ\
+cEhZcwAALiMAAC4jAXilP3YAAAAHdElNRQfnAx0BLBeZZvBWAAAAGXRFWHRDb21tZW50AENyZWF0\
+ZWQgd2l0aCBHSU1QV4EOFwAAACpJREFUGNNj/M/A8J+BgYGB4T+EYmBkZMDGZ2IgErAQMgnGJ9pE\
+xhHpRgAVIB4MSL68ZgAAAABJRU5ErkJggg==");
     bounds: 0 0 100 100;
     filter: nearest;
   }