Make border radii clip their contents.

Needed for browser.html rounded corners.

components/gfx/display_list/mod.rs

@@ -762,9 +762,7 @@ pub struct BaseDisplayItem {
 
 impl BaseDisplayItem {
     #[inline(always)]
-    pub fn new(bounds: &Rect<Au>,
-               metadata: DisplayItemMetadata,
-               clip: &ClippingRegion)
+    pub fn new(bounds: &Rect<Au>, metadata: DisplayItemMetadata, clip: &ClippingRegion)
                -> BaseDisplayItem {
         // Detect useless clipping regions here and optimize them to `ClippingRegion::max()`.
         // The painting backend may want to optimize out clipping regions and this makes it easier
@@ -887,13 +885,11 @@ impl ClippingRegion {
 
     /// Intersects this clipping region with the given rounded rectangle.
     #[inline]
-    pub fn intersect_with_rounded_rect(mut self, rect: &Rect<Au>, radii: &BorderRadii<Au>)
-                                       -> ClippingRegion {
+    pub fn intersect_with_rounded_rect(&mut self, rect: &Rect<Au>, radii: &BorderRadii<Au>) {
         self.complex.push(ComplexClippingRegion {
             rect: *rect,
             radii: *radii,
         });
-        self
     }
 
     /// Translates this clipping region by the given vector.

components/layout/display_list_builder.rs

@@ -335,7 +335,7 @@ impl FragmentDisplayListBuilding for Fragment {
         let border_radii = build_border_radius(absolute_bounds, style.get_border());
         let mut clip = (*clip).clone();
         if !border_radii.is_square() {
-            clip = clip.intersect_with_rounded_rect(absolute_bounds, &border_radii)
+            clip.intersect_with_rounded_rect(absolute_bounds, &border_radii)
         }
 
         // FIXME: This causes a lot of background colors to be displayed when they are clearly not
@@ -1473,6 +1473,12 @@ impl FragmentDisplayListBuilding for Fragment {
             }
             _ => {}
         }
+
+        let border_radii = build_border_radius(stacking_relative_border_box,
+                                               self.style.get_border());
+        if !border_radii.is_square() {
+            current_clip.intersect_with_rounded_rect(stacking_relative_border_box, &border_radii)
+        }
     }
 
     fn build_display_list_for_text_fragment(&self,