Update WR (pixel snapping improvements).

This includes a WR update that improves pixel snapping. Specifically,
the non-transform shader now snaps to device pixels in world space,
rather than local space.

This makes 31 new tests pass, and adds 4 new failures.

Of the new failures:
 - The three background size tests appear to be an OSMesa accuracy
   issue. Near the bottom of the image, a small number of pixels
   are different from the reference by a value of 1.0 / 255.0. I've
   confirmed on 3 real GPUs and also on llvmpipe that the tests
   match on those devices. This would be a good case for fuzzy test
   support in WPT.
 - The other failing test appears to have unreasonable accuracy
   requirements as it also fails on Gecko and Chromium in the same
   way that the test now fails on WR.

components/compositing/compositor.rs

@@ -734,7 +734,7 @@ impl<Window: WindowMethods> IOCompositor<Window> {
 
         let pipeline_id = frame_tree.pipeline.id.to_webrender();
         self.webrender_api.set_root_pipeline(pipeline_id);
-        self.webrender_api.generate_frame();
+        self.webrender_api.generate_frame(None);
 
         self.create_pipeline_details_for_frame_tree(&frame_tree);
 

components/layout/webrender_helpers.rs

@@ -184,7 +184,7 @@ impl ToFilterOps for filter::T {
                 Filter::Grayscale(amount) => result.push(webrender_traits::FilterOp::Grayscale(amount)),
                 Filter::HueRotate(angle) => result.push(webrender_traits::FilterOp::HueRotate(angle.0)),
                 Filter::Invert(amount) => result.push(webrender_traits::FilterOp::Invert(amount)),
-                Filter::Opacity(amount) => result.push(webrender_traits::FilterOp::Opacity(amount)),
+                Filter::Opacity(amount) => result.push(webrender_traits::FilterOp::Opacity(amount.into())),
                 Filter::Saturate(amount) => result.push(webrender_traits::FilterOp::Saturate(amount)),
                 Filter::Sepia(amount) => result.push(webrender_traits::FilterOp::Sepia(amount)),
             }
@@ -347,8 +347,8 @@ impl WebRenderDisplayItemConverter for DisplayItem {
                                               stacking_context.bounds.to_rectf(),
                                               clip,
                                               stacking_context.z_index,
-                                              &LayoutTransform::from_untyped(&stacking_context.transform),
-                                              &LayoutTransform::from_untyped(&stacking_context.perspective),
+                                              LayoutTransform::from_untyped(&stacking_context.transform).into(),
+                                              LayoutTransform::from_untyped(&stacking_context.perspective),
                                               stacking_context.blend_mode.to_blend_mode(),
                                               stacking_context.filters.to_filter_ops());
             }

components/layout_thread/lib.rs

@@ -989,7 +989,7 @@ impl LayoutThread {
                 viewport_size,
                 builder,
                 true);
-            self.webrender_api.generate_frame();
+            self.webrender_api.generate_frame(None);
         });
     }
 

components/servo/lib.rs

@@ -184,6 +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,
+                workers: None,
             }).expect("Unable to initialize webrender!")
         };
 

tests/wpt/metadata-css/css-transforms-1_dev/html/transform-input-019.htm.ini → tests/wpt/metadata-css/css-backgrounds-3_dev/html4/background-size-025.htm.ini

@@ -1,3 +1,3 @@
-[transform-input-019.htm]
+[background-size-025.htm]
   type: reftest
   expected: FAIL

tests/wpt/metadata-css/css21_dev/html4/abspos-008.htm.ini → tests/wpt/metadata-css/css-backgrounds-3_dev/html4/background-size-028.htm.ini

@@ -1,4 +1,4 @@
-[abspos-008.htm]
+[background-size-028.htm]
   type: reftest
   expected:
     if os == "linux": FAIL

tests/wpt/metadata-css/css-transforms-1_dev/html/transform-input-017.htm.ini → tests/wpt/metadata-css/css-backgrounds-3_dev/html4/background-size-030.htm.ini

@@ -1,4 +1,4 @@
-[transform-input-017.htm]
+[background-size-030.htm]
   type: reftest
   expected:
     if os == "linux": FAIL

tests/wpt/metadata-css/css-backgrounds-3_dev/html4/background-size-contain.htm.ini → tests/wpt/metadata-css/css21_dev/html4/c5525-fltmrgn-000.htm.ini

@@ -1,3 +1,3 @@
-[background-size-contain.htm]
+[c5525-fltmrgn-000.htm]
   type: reftest
   expected: FAIL