diff --git a/layout/style/nsCSSParser.cpp b/layout/style/nsCSSParser.cpp
index 92cc84a7c1..376df8aab4 100644
--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -137,6 +137,22 @@ struct CSSParserInputState {
   bool mHavePushBack;
 };
 
+struct ReduceNumberCalcOps : public mozilla::css::BasicFloatCalcOps,
+                             public mozilla::css::CSSValueInputCalcOps
+{
+  result_type ComputeLeafValue(const nsCSSValue& aValue)
+  {
+    // FIXME: Restore this assertion once ParseColor no longer uses this class.
+    //MOZ_ASSERT(aValue.GetUnit() == eCSSUnit_Number, "unexpected unit");
+    return aValue.GetFloatValue();
+  }
+
+  float ComputeNumber(const nsCSSValue& aValue)
+  {
+    return mozilla::css::ComputeCalc(aValue, *this);
+  }
+};
+
 static_assert(css::eAuthorSheetFeatures == 0 &&
               css::eUserSheetFeatures == 1 &&
               css::eAgentSheetFeatures == 2,
@@ -896,6 +912,7 @@ protected:
   };
 
   bool IsFunctionTokenValidForImageLayerImage(const nsCSSToken& aToken) const;
+  bool IsCalcFunctionToken(const nsCSSToken& aToken) const;
   bool ParseImageLayersItem(ImageLayersShorthandParseState& aState,
                             const nsCSSPropertyID aTable[]);
 
@@ -7874,14 +7891,6 @@ CSSParserImpl::ParseOneOrLargerVariant(nsCSSValue& aValue,
   return result;
 }
 
-static bool
-IsCSSTokenCalcFunction(const nsCSSToken& aToken)
-{
-  return aToken.mType == eCSSToken_Function &&
-         (aToken.mIdent.LowerCaseEqualsLiteral("calc") ||
-          aToken.mIdent.LowerCaseEqualsLiteral("-moz-calc"));
-}
-
 // Assigns to aValue iff it returns CSSParseResult::Ok.
 CSSParseResult
 CSSParserImpl::ParseVariant(nsCSSValue& aValue,
@@ -8181,7 +8190,7 @@ CSSParserImpl::ParseVariant(nsCSSValue& aValue,
     }
   }
   if ((aVariantMask & VARIANT_CALC) &&
-      IsCSSTokenCalcFunction(*tk)) {
+      IsCalcFunctionToken(*tk)) {
     // calc() currently allows only lengths and percents and number inside it.
     // And note that in current implementation, number cannot be mixed with
     // length and percent.
@@ -12430,6 +12439,14 @@ CSSParserImpl::IsFunctionTokenValidForImageLayerImage(
       funcName.LowerCaseEqualsLiteral("-webkit-repeating-radial-gradient")));
 }
 
+bool
+CSSParserImpl::IsCalcFunctionToken(const nsCSSToken& aToken) const
+{
+  return aToken.mType == eCSSToken_Function &&
+         (aToken.mIdent.LowerCaseEqualsLiteral("calc") ||
+          aToken.mIdent.LowerCaseEqualsLiteral("-moz-calc"));
+}
+
 // Parse one item of the background shorthand property.
 bool
 CSSParserImpl::ParseImageLayersItem(
@@ -13822,21 +13839,6 @@ CSSParserImpl::ParseCalcAdditiveExpression(nsCSSValue& aValue,
   }
 }
 
-struct ReduceNumberCalcOps : public mozilla::css::BasicFloatCalcOps,
-                             public mozilla::css::CSSValueInputCalcOps
-{
-  result_type ComputeLeafValue(const nsCSSValue& aValue)
-  {
-    MOZ_ASSERT(aValue.GetUnit() == eCSSUnit_Number, "unexpected unit");
-    return aValue.GetFloatValue();
-  }
-
-  float ComputeNumber(const nsCSSValue& aValue)
-  {
-    return mozilla::css::ComputeCalc(aValue, *this);
-  }
-};
-
 //  * If aVariantMask is VARIANT_NUMBER, this function parses the
 //    <number-multiplicative-expression> production.
 //  * If aVariantMask does not contain VARIANT_NUMBER, this function
@@ -13957,7 +13959,7 @@ CSSParserImpl::ParseCalcTerm(nsCSSValue& aValue, uint32_t& aVariantMask)
   // Either an additive expression in parentheses...
   if (mToken.IsSymbol('(') ||
       // Treat nested calc() as plain parenthesis.
-      IsCSSTokenCalcFunction(mToken)) {
+      IsCalcFunctionToken(mToken)) {
     if (!ParseCalcAdditiveExpression(aValue, aVariantMask) ||
         !ExpectSymbol(')', true)) {
       SkipUntil(')');