Auto merge of #18926 - glennw:update-wr-bs, r=<try>

Update WR (box shadows, subpixel + alpha text)

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components/gfx/display_list/mod.rs

@@ -1153,8 +1153,6 @@ pub struct DefineClipScrollNodeItem {
 /// How a box shadow should be clipped.
 #[derive(Clone, Copy, Debug, Deserialize, HeapSizeOf, PartialEq, Serialize)]
 pub enum BoxShadowClipMode {
-    /// No special clipping should occur. This is used for (shadowed) text decorations.
-    None,
     /// The area inside `box_bounds` should be clipped out. Corresponds to the normal CSS
     /// `box-shadow`.
     Outset,

components/layout/webrender_helpers.rs

@@ -73,7 +73,6 @@ trait ToBoxShadowClipMode {
 impl ToBoxShadowClipMode for BoxShadowClipMode {
     fn to_clip_mode(&self) -> webrender_api::BoxShadowClipMode {
         match *self {
-            BoxShadowClipMode::None => webrender_api::BoxShadowClipMode::None,
             BoxShadowClipMode::Inset => webrender_api::BoxShadowClipMode::Inset,
             BoxShadowClipMode::Outset => webrender_api::BoxShadowClipMode::Outset,
         }

tests/wpt/metadata-css/css-backgrounds-3_dev/html4/css3-box-shadow.htm.ini

@@ -0,0 +1,5 @@
+[css3-box-shadow.htm]
+  type: reftest
+  expected:
+    if os == "linux": FAIL
+  bug: https://github.com/servo/webrender/issues/1776