[mathml] Fix logic errors in linethickness interpretation

The linethickness property should be parsed as length-percentage [1, 2],
so add a method to CSSParser to parse length-percentage. Negative
values are allowed as length-percentage but are clamped to zero by
the FractionLineThickness method.
Finally, for now we do not accept calc() expressions.

[1] https://mathml-refresh.github.io/mathml-core/#dfn-linethickness
[2] https://mathml-refresh.github.io/mathml-core/#dfn-length-percentage

Bug: 6606
Change-Id: I621d17d6e69cc113016fe1c809f55776c7e357d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2098728Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Reviewed-by: Mason Freed <masonfreed@chromium.org>
Reviewed-by: Frédéric Wang <fwang@igalia.com>
Commit-Queue: Rob Buis <rbuis@igalia.com>
Cr-Commit-Position: refs/heads/master@{#754546}

third_party/blink/renderer/core/css/parser/css_parser.cc

@@ -11,6 +11,7 @@
 #include "third_party/blink/renderer/core/css/parser/css_parser_fast_paths.h"
 #include "third_party/blink/renderer/core/css/parser/css_parser_impl.h"
 #include "third_party/blink/renderer/core/css/parser/css_property_parser.h"
+#include "third_party/blink/renderer/core/css/parser/css_property_parser_helpers.h"
 #include "third_party/blink/renderer/core/css/parser/css_selector_parser.h"
 #include "third_party/blink/renderer/core/css/parser/css_supports_parser.h"
 #include "third_party/blink/renderer/core/css/parser/css_tokenizer.h"
@@ -275,4 +276,16 @@ const CSSValue* CSSParser::ParseFontFaceDescriptor(
   return value;
 }
 
+CSSPrimitiveValue* CSSParser::ParseLengthPercentage(
+    const String& string,
+    const CSSParserContext* context) {
+  if (string.IsEmpty() || !context)
+    return nullptr;
+  CSSTokenizer tokenizer(string);
+  const auto tokens = tokenizer.TokenizeToEOF();
+  CSSParserTokenRange range(tokens);
+  return css_property_parser_helpers::ConsumeLengthOrPercent(range, *context,
+                                                             kValueRangeAll);
+}
+
 }  // namespace blink

third_party/blink/renderer/core/css/parser/css_parser.h

@@ -23,6 +23,7 @@ class StyleRuleBase;
 class StyleRuleKeyframe;
 class StyleSheetContents;
 class CSSValue;
+class CSSPrimitiveValue;
 enum class ParseSheetResult;
 enum class SecureContextMode;
 
@@ -112,6 +113,9 @@ class CORE_EXPORT CSSParser {
                                                const String&,
                                                CSSParserObserver&);
 
+  static CSSPrimitiveValue* ParseLengthPercentage(const String&,
+                                                  const CSSParserContext*);
+
  private:
   static MutableCSSPropertyValueSet::SetResult ParseValue(
       MutableCSSPropertyValueSet*,

third_party/blink/renderer/core/mathml/mathml_element.cc

@@ -111,14 +111,12 @@ base::Optional<Length> MathMLElement::AddMathLengthToComputedStyle(
     const QualifiedName& attr_name) {
   if (!FastHasAttribute(attr_name))
     return base::nullopt;
-  auto string = FastGetAttribute(attr_name);
-  const CSSValue* parsed = CSSParser::ParseSingleValue(
-      CSSPropertyID::kHeight, string,
-      StrictCSSParserContext(GetDocument().GetSecureContextMode()));
-  const auto* new_value = DynamicTo<CSSPrimitiveValue>(parsed);
-  if (!new_value || !new_value->IsLength())
+  auto value = FastGetAttribute(attr_name);
+  const CSSPrimitiveValue* parsed_value = CSSParser::ParseLengthPercentage(
+      value, StrictCSSParserContext(GetDocument().GetSecureContextMode()));
+  if (!parsed_value || parsed_value->IsCalculated())
     return base::nullopt;
-  return new_value->ConvertToLength(conversion_data);
+  return parsed_value->ConvertToLength(conversion_data);
 }
 
 }  // namespace blink

third_party/blink/web_tests/TestExpectations

@@ -1627,7 +1627,6 @@ crbug.com/875235 virtual/layout_ng_fieldset/fast/forms/fieldset/legend-after-mar
 crbug.com/6606 external/wpt/mathml/presentation-markup/direction/direction-006.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/direction/direction-009.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/direction/direction.html [ Failure ]
-crbug.com/6606 external/wpt/mathml/presentation-markup/fractions/frac-linethickness-002.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/fractions/frac-parameters-gap-001.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/fractions/frac-parameters-gap-002.html [ Failure ]
 crbug.com/6606 external/wpt/mathml/presentation-markup/fractions/frac-parameters-gap-003.html [ Failure ]

third_party/blink/web_tests/external/wpt/mathml/presentation-markup/fractions/frac-linethickness-002.html

@@ -56,6 +56,12 @@
           assert_approx_equals(LineThickness("namedspace"), defaultRuleThickness, epsilon);
         }, "Named space");
 
+        test(function() {
+          assert_true(MathMLFeatureDetection.has_mspace());
+          /* Calc() expressions are invalid in MathML Core. */
+          assert_approx_equals(LineThickness("calc"), defaultRuleThickness, epsilon);
+        }, "Calc() expression");
+
         done();
       }
     </script>
@@ -85,5 +91,11 @@
         <mspace width="20px" height="10px" style="background: cyan"></mspace>
       </mfrac>
     </math>
+    <math>
+      <mfrac id="calc" linethickness="calc(20px)">
+        <mspace width="20px" height="10px" style="background: blue"></mspace>
+        <mspace width="20px" height="10px" style="background: cyan"></mspace>
+      </mfrac>
+    </math>
   </body>
 </html>