LibWeb: Set blur filter radius to 0px if omitted

Libraries/LibWeb/CSS/StyleValues/FilterValueListStyleValue.cpp

@@ -15,11 +15,7 @@ namespace Web::CSS {
 
 float FilterOperation::Blur::resolved_radius(Layout::Node const& node) const
 {
-    if (radius.has_value())
-        return radius->resolved({ .length_resolution_context = Length::ResolutionContext::for_layout_node(node) })->to_px(node).to_float();
-
-    // Default value when omitted is 0px.
-    return 0;
+    return radius.resolved({ .length_resolution_context = Length::ResolutionContext::for_layout_node(node) })->to_px(node).to_float();
 }
 
 float FilterOperation::HueRotate::angle_degrees(Layout::Node const& node) const
@@ -56,9 +52,7 @@ String FilterValueListStyleValue::to_string(SerializationMode) const
             builder.append(' ');
         filter_function.visit(
             [&](FilterOperation::Blur const& blur) {
-                builder.append("blur("sv);
-                if (blur.radius.has_value())
-                    builder.append(blur.radius->to_string());
+                builder.appendff("blur({}"sv, blur.radius.to_string());
             },
             [&](FilterOperation::DropShadow const& drop_shadow) {
                 builder.appendff("drop-shadow("sv);

Libraries/LibWeb/CSS/StyleValues/FilterValueListStyleValue.h

@@ -21,7 +21,7 @@ namespace Web::CSS {
 namespace FilterOperation {
 
 struct Blur {
-    Optional<LengthOrCalculated> radius;
+    LengthOrCalculated radius { Length::make_px(0) };
     float resolved_radius(Layout::Node const&) const;
     bool operator==(Blur const&) const = default;
 };

Tests/LibWeb/Text/expected/wpt-import/css/filter-effects/parsing/filter-computed.txt

@@ -2,11 +2,11 @@ Harness status: OK
 
 Found 34 tests
 
-17 Pass
-17 Fail
+18 Pass
+16 Fail
 Pass	Property filter value 'none'
 Pass	Property filter value 'blur(100px)'
-Fail	Property filter value 'blur()'
+Pass	Property filter value 'blur()'
 Pass	Property filter value 'brightness(0)'
 Fail	Property filter value 'brightness(300%)'
 Pass	Property filter value 'brightness()'