Fix usage counter for calculated unitless SVG length

The original counter only counts unitless length literals, which is
incorrect and was exposed by a recent refactoring crrev.com/c/1696274

This patch changes the counter to also count unitless lengths involved
in math functions (e.g., calc(1 + 1%)).

Bug: 979895
Change-Id: I49744bceee307485e979addb3ea9be95d9d22922
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1750189Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Fredrik Söderquist <fs@opera.com>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686493}

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

@@ -461,14 +461,24 @@ CSSPrimitiveValue* ConsumeLengthOrPercent(CSSParserTokenRange& range,
 namespace {
 
 bool IsNonZeroUserUnitsValue(const CSSPrimitiveValue* value) {
-  // TODO(crbug.com/979895): This is the result of a refactoring, which might
-  // have revealed an existing bug in handling user units in math functions. Fix
-  // it if necessary.
-  const auto* numeric_literal = DynamicTo<CSSNumericLiteralValue>(value);
-  return numeric_literal &&
-         numeric_literal->GetType() ==
-             CSSPrimitiveValue::UnitType::kUserUnits &&
-         value->GetDoubleValue() != 0;
+  if (!value)
+    return false;
+  if (const auto* numeric_literal = DynamicTo<CSSNumericLiteralValue>(value)) {
+    return numeric_literal->GetType() ==
+               CSSPrimitiveValue::UnitType::kUserUnits &&
+           value->GetDoubleValue() != 0;
+  }
+  const auto& math_value = To<CSSMathFunctionValue>(*value);
+  switch (math_value.Category()) {
+    case kCalcNumber:
+      return math_value.DoubleValue() != 0;
+    case kCalcPercentNumber:
+    case kCalcLengthNumber:
+    case kCalcPercentLengthNumber:
+      return true;
+    default:
+      return false;
+  }
 }
 
 }  // namespace