Update WR.

- Subpixel positioning improvements.
- Clipping fixes and optimizations.
- Fix panic when transform can't be inverted.
- Support multiple filters on single stacking context.
- Optimize gradients, support unlimited stops.
- Add external image + texture cache support.
- Support error path on shader compile error.
- Optimize border handling in texture atlas.
- Preliminary work towards clip/scroll root changes.

components/servo/lib.rs

@@ -184,7 +184,7 @@ impl<Window> Browser<Window> where Window: WindowMethods + 'static {
                 clear_framebuffer: true,
                 clear_color: webrender_traits::ColorF::new(1.0, 1.0, 1.0, 1.0),
                 render_target_debug: false,
-            }).unwrap()
+            }).expect("Unable to initialize webrender!")
         };
 
         // Important that this call is done in a single-threaded fashion, we