Bug 1477551 - Ensure the clip and the rect that we push for bullets agree. r=jrmuizel

Using mPathRect causes rounding errors unnecessarily.

Differential Revision: https://phabricator.services.mozilla.com/D5698

gfx/webrender_bindings/WebRenderTypes.h

@@ -371,6 +371,19 @@ static inline wr::ComplexClipRegion ToComplexClipRegion(const gfx::RoundedRect&
   return ret;
 }
 
+static inline wr::ComplexClipRegion SimpleRadii(const wr::LayoutRect& aRect, float aRadii)
+{
+  wr::ComplexClipRegion ret;
+  wr::LayoutSize radii { aRadii, aRadii };
+  ret.rect = aRect;
+  ret.radii.top_left = radii;
+  ret.radii.top_right = radii;
+  ret.radii.bottom_left = radii;
+  ret.radii.bottom_right = radii;
+  ret.mode = wr::ClipMode::Clip;
+  return ret;
+}
+
 static inline wr::LayoutSize ToLayoutSize(const mozilla::LayoutDeviceIntSize& size)
 {
   return ToLayoutSize(LayoutDeviceSize(size));

layout/generic/nsBulletFrame.cpp

@@ -527,11 +527,8 @@ BulletRenderer::CreateWebRenderCommandsForPath(nsDisplayItem* aItem,
       return true;
     }
     case NS_STYLE_LIST_STYLE_DISC: {
-      nsTArray<wr::ComplexClipRegion> clips;
-      clips.AppendElement(wr::ToComplexClipRegion(
-        RoundedRect(mPathRect.ToUnknownRect(),
-                    RectCornerRadii(dest.size.width / 2.0))
-      ));
+      AutoTArray<wr::ComplexClipRegion, 1> clips;
+      clips.AppendElement(wr::SimpleRadii(dest, dest.size.width / 2));
       auto clipId = aBuilder.DefineClip(Nothing(), dest, &clips, nullptr);
       aBuilder.PushClip(clipId);
       aBuilder.PushRect(dest, dest, isBackfaceVisible, color);