A sizes attribute parser

Source/core/css/CSSPrimitiveValue.cpp

Index: Source/core/css/CSSPrimitiveValue.cpp
diff --git a/Source/core/css/CSSPrimitiveValue.cpp b/Source/core/css/CSSPrimitiveValue.cpp
index 2b1f3bd43b8f7789a69672e73c0fd21ed6a48e65..3e8650402d00f0b210d388a06343b4215de8ccc1 100644
--- a/Source/core/css/CSSPrimitiveValue.cpp
+++ b/Source/core/css/CSSPrimitiveValue.cpp
@@ -611,6 +611,9 @@ template<> double CSSPrimitiveValue::computeLength(const CSSToLengthConversionDa
 
 double CSSPrimitiveValue::computeLengthDouble(const CSSToLengthConversionData& conversionData)
 {
+    // The logic in this function is duplicated in MediaValues::computeLength
+    // because MediaValues::computeLength needs nearly identical logic, but we haven't found a way to make
+    // CSSPrimitiveValue::computeLengthDouble more generic (to solve both cases) without hurting performance.
     if (m_primitiveUnitType == CSS_CALC)
         return m_value.calc->computeLengthPx(conversionData);