Fix rendering of dotted corners when corner radius < border width.

webrender/Cargo.toml

@@ -17,7 +17,7 @@ query = []
 app_units = "0.5.6"
 bincode = "0.9"
 byteorder = "1.0"
-euclid = "0.15.2"
+euclid = "0.15.5"
 fxhash = "0.2.1"
 gleam = "0.4.8"
 lazy_static = "0.2"

webrender/src/border.rs

@@ -555,7 +555,7 @@ impl BorderCornerClipSource {
             BorderCornerClipKind::Dot => {
                 // The centers of dots follow an ellipse along the middle of the
                 // border radius.
-                let inner_radius = corner_radius - widths * 0.5;
+                let inner_radius = (corner_radius - widths * 0.5).abs();
                 let ellipse = Ellipse::new(inner_radius);
 
                 // Allocate a "worst case" number of dot clips. This can be

wrench/reftests/border/dotted-corner-small-radius.yaml

@@ -0,0 +1,12 @@
+---
+root: 
+  items: 
+    - bounds: [5, 5, 490, 490]
+      "clip-rect": [5, 5, 490, 490]
+      "clip-and-scroll": 0
+      "backface-visible": true
+      type: border
+      width: 25
+      "border-type": normal
+      color: black
+      style: dotted

wrench/reftests/border/reftest.list

@@ -13,3 +13,4 @@ fuzzy(255,24) == border-ridge-simple.yaml border-ridge-simple-ref.yaml
 == border-image-crash.yaml border-image-crash-ref.yaml
 == border-image-fill.yaml border-image-fill-ref.png
 == border-no-bogus-line.yaml border-no-bogus-line-ref.png
+== dotted-corner-small-radius.yaml dotted-corner-small-radius.png