--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -926,17 +926,17 @@ already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetStackSizing()
 {
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
   val->SetIdent(StyleXUL()->mStretchStack ? eCSSKeyword_stretch_to_fit :
                 eCSSKeyword_ignore);
   return val.forget();
 }
 
-void
+/* static */ void
 nsComputedDOMStyle::SetToRGBAColor(nsROCSSPrimitiveValue* aValue,
                                    nscolor aColor)
 {
   if (NS_GET_A(aColor) == 0) {
     aValue->SetIdent(eCSSKeyword_transparent);
     return;
   }
 
@@ -1222,30 +1222,29 @@ nsComputedDOMStyle::DoGetTransformOrigin
 
   /* Store things as a value list */
   RefPtr<nsDOMCSSValueList> valueList = GetROCSSValueList(false);
 
   /* Now, get the values. */
   const nsStyleDisplay* display = StyleDisplay();
 
   RefPtr<nsROCSSPrimitiveValue> width = new nsROCSSPrimitiveValue;
-  SetValueToCoord(width, display->mTransformOrigin[0], false,
+  SetValueToCoord(width, display->mTransformOrigin[0], false, this,
                   &nsComputedDOMStyle::GetFrameBoundsWidthForTransform);
   valueList->AppendCSSValue(width.forget());
 
   RefPtr<nsROCSSPrimitiveValue> height = new nsROCSSPrimitiveValue;
-  SetValueToCoord(height, display->mTransformOrigin[1], false,
+  SetValueToCoord(height, display->mTransformOrigin[1], false, this,
                   &nsComputedDOMStyle::GetFrameBoundsHeightForTransform);
   valueList->AppendCSSValue(height.forget());
 
   if (display->mTransformOrigin[2].GetUnit() != eStyleUnit_Coord ||
       display->mTransformOrigin[2].GetCoordValue() != 0) {
     RefPtr<nsROCSSPrimitiveValue> depth = new nsROCSSPrimitiveValue;
-    SetValueToCoord(depth, display->mTransformOrigin[2], false,
-                    nullptr);
+    SetValueToCoord(depth, display->mTransformOrigin[2], false);
     valueList->AppendCSSValue(depth.forget());
   }
 
   return valueList.forget();
 }
 
 /* Convert the stored representation into a list of two values and then hand
  * it back.
@@ -1259,22 +1258,22 @@ nsComputedDOMStyle::DoGetPerspectiveOrig
 
   /* Store things as a value list */
   RefPtr<nsDOMCSSValueList> valueList = GetROCSSValueList(false);
 
   /* Now, get the values. */
   const nsStyleDisplay* display = StyleDisplay();
 
   RefPtr<nsROCSSPrimitiveValue> width = new nsROCSSPrimitiveValue;
-  SetValueToCoord(width, display->mPerspectiveOrigin[0], false,
+  SetValueToCoord(width, display->mPerspectiveOrigin[0], false, this,
                   &nsComputedDOMStyle::GetFrameBoundsWidthForTransform);
   valueList->AppendCSSValue(width.forget());
 
   RefPtr<nsROCSSPrimitiveValue> height = new nsROCSSPrimitiveValue;
-  SetValueToCoord(height, display->mPerspectiveOrigin[1], false,
+  SetValueToCoord(height, display->mPerspectiveOrigin[1], false, this,
                   &nsComputedDOMStyle::GetFrameBoundsHeightForTransform);
   valueList->AppendCSSValue(height.forget());
 
   return valueList.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetPerspective()
@@ -1914,17 +1913,17 @@ AppendCSSGradientToBoxPosition(const nsS
     aString.AppendLiteral(" right");
   } else if (xValue != 0.5f) { // do not write "center" keyword
     NS_NOTREACHED("invalid box position");
   }
 
   aNeedSep = true;
 }
 
-void
+/* static */ void
 nsComputedDOMStyle::GetCSSGradientString(const nsStyleGradient* aGradient,
                                          nsAString& aString)
 {
   if (!aGradient->mLegacySyntax) {
     aString.Truncate();
   } else {
     aString.AssignLiteral("-moz-");
   }
@@ -2045,17 +2044,17 @@ nsComputedDOMStyle::GetCSSGradientString
     }
     needSep = true;
   }
 
   aString.Append(')');
 }
 
 // -moz-image-rect(<uri>, <top>, <right>, <bottom>, <left>)
-void
+/* static */ void
 nsComputedDOMStyle::GetImageRectString(nsIURI* aURI,
                                        const nsStyleSides& aCropRect,
                                        nsString& aString)
 {
   RefPtr<nsDOMCSSValueList> valueList = GetROCSSValueList(true);
 
   // <uri>
   RefPtr<nsROCSSPrimitiveValue> valURI = new nsROCSSPrimitiveValue;
@@ -2072,42 +2071,44 @@ nsComputedDOMStyle::GetImageRectString(n
   nsAutoString argumentString;
   valueList->GetCssText(argumentString);
 
   aString = NS_LITERAL_STRING("-moz-image-rect(") +
             argumentString +
             NS_LITERAL_STRING(")");
 }
 
+namespace mozilla {
+
 void
-nsComputedDOMStyle::SetValueToStyleImage(const nsStyleImage& aStyleImage,
-                                         nsROCSSPrimitiveValue* aValue)
+SetValueToStyleImage(const nsStyleImage& aStyleImage,
+                     nsROCSSPrimitiveValue* aValue)
 {
   switch (aStyleImage.GetType()) {
     case eStyleImageType_Image:
     {
       imgIRequest *req = aStyleImage.GetImageData();
       nsCOMPtr<nsIURI> uri;
       req->GetURI(getter_AddRefs(uri));
 
       const UniquePtr<nsStyleSides>& cropRect = aStyleImage.GetCropRect();
       if (cropRect) {
         nsAutoString imageRectString;
-        GetImageRectString(uri, *cropRect, imageRectString);
+        nsComputedDOMStyle::GetImageRectString(uri, *cropRect, imageRectString);
         aValue->SetString(imageRectString);
       } else {
         aValue->SetURI(uri);
       }
       break;
     }
     case eStyleImageType_Gradient:
     {
       nsAutoString gradientString;
-      GetCSSGradientString(aStyleImage.GetGradientData(),
-                           gradientString);
+      nsComputedDOMStyle::GetCSSGradientString(aStyleImage.GetGradientData(),
+                                               gradientString);
       aValue->SetString(gradientString);
       break;
     }
     case eStyleImageType_Element:
     {
       nsAutoString elementId;
       nsStyleUtil::AppendEscapedCSSIdent(
         nsDependentString(aStyleImage.GetElementId()), elementId);
@@ -2121,16 +2122,18 @@ nsComputedDOMStyle::SetValueToStyleImage
       aValue->SetIdent(eCSSKeyword_none);
       break;
     default:
       NS_NOTREACHED("unexpected image type");
       break;
   }
 }
 
+} // namespace mozilla
+
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetImageLayerImage(const nsStyleImageLayers& aLayers)
 {
   RefPtr<nsDOMCSSValueList> valueList = GetROCSSValueList(true);
 
   for (uint32_t i = 0, i_end = aLayers.mImageCount; i < i_end; ++i) {
     RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
 
@@ -2145,17 +2148,17 @@ nsComputedDOMStyle::DoGetImageLayerImage
     //    Instead, we store the local URI in one place -- on Layer::mSourceURI.
     //    Hence, we must serialize using mSourceURI (instead of
     //    SetValueToStyleImage()/mImage) in this case.
     if (aLayers.mLayers[i].mSourceURI.IsLocalRef()) {
       // This is how we represent a 'mask-image' reference for a local URI,
       // such as 'mask-image:url(#mymask)' or 'mask:url(#mymask)'
       SetValueToFragmentOrURL(&aLayers.mLayers[i].mSourceURI, val);
     } else {
-      SetValueToStyleImage(image, val);
+      mozilla::SetValueToStyleImage(image, val);
     }
 
     valueList->AppendCSSValue(val.forget());
   }
 
   return valueList.forget();
 }
 
@@ -2528,34 +2531,34 @@ nsComputedDOMStyle::AppendGridLineNames(
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::GetGridTrackSize(const nsStyleCoord& aMinValue,
                                      const nsStyleCoord& aMaxValue)
 {
   if (aMinValue == aMaxValue) {
     RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
-    SetValueToCoord(val, aMinValue, true,
-                    nullptr, nsCSSProps::kGridTrackBreadthKTable);
+    SetValueToCoord(val, aMinValue, true, nullptr, nullptr,
+                    nsCSSProps::kGridTrackBreadthKTable);
     return val.forget();
   }
 
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
   nsAutoString argumentStr, minmaxStr;
   minmaxStr.AppendLiteral("minmax(");
 
-  SetValueToCoord(val, aMinValue, true,
-                  nullptr, nsCSSProps::kGridTrackBreadthKTable);
+  SetValueToCoord(val, aMinValue, true, nullptr, nullptr,
+                  nsCSSProps::kGridTrackBreadthKTable);
   val->GetCssText(argumentStr);
   minmaxStr.Append(argumentStr);
 
   minmaxStr.AppendLiteral(", ");
 
-  SetValueToCoord(val, aMaxValue, true,
-                  nullptr, nsCSSProps::kGridTrackBreadthKTable);
+  SetValueToCoord(val, aMaxValue, true, nullptr, nullptr,
+                  nsCSSProps::kGridTrackBreadthKTable);
   val->GetCssText(argumentStr);
   minmaxStr.Append(argumentStr);
 
   minmaxStr.Append(char16_t(')'));
   val->SetString(minmaxStr);
   return val.forget();
 }
 
@@ -3587,17 +3590,17 @@ nsComputedDOMStyle::DoGetLineHeight()
 {
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
 
   nscoord lineHeight;
   if (GetLineHeightCoord(lineHeight)) {
     val->SetAppUnits(lineHeight);
   } else {
     SetValueToCoord(val, StyleText()->mLineHeight, true,
-                    nullptr, nsCSSProps::kLineHeightKTable);
+                    nullptr, nullptr, nsCSSProps::kLineHeightKTable);
   }
 
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetRubyAlign()
 {
@@ -3616,16 +3619,17 @@ nsComputedDOMStyle::DoGetRubyPosition()
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetVerticalAlign()
 {
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
   SetValueToCoord(val, StyleDisplay()->mVerticalAlign, false,
+                  this,
                   &nsComputedDOMStyle::GetLineHeightCoord,
                   nsCSSProps::kVerticalAlignKTable);
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::CreateTextAlignValue(uint8_t aAlign, bool aAlignTrue,
                                          const KTableEntry aTable[])
@@ -3835,17 +3839,17 @@ nsComputedDOMStyle::DoGetTextEmphasisSty
   valueList->AppendCSSValue(shapeVal.forget());
   return valueList.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetTextIndent()
 {
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
-  SetValueToCoord(val, StyleText()->mTextIndent, false,
+  SetValueToCoord(val, StyleText()->mTextIndent, false, this,
                   &nsComputedDOMStyle::GetCBContentWidth);
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetTextOrientation()
 {
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
@@ -4204,31 +4208,31 @@ nsComputedDOMStyle::DoGetBoxSizing()
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetBorderImageSource()
 {
   const nsStyleBorder* border = StyleBorder();
 
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
   const nsStyleImage& image = border->mBorderImageSource;
-  SetValueToStyleImage(image, val);
+  mozilla::SetValueToStyleImage(image, val);
 
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetBorderImageSlice()
 {
   RefPtr<nsDOMCSSValueList> valueList = GetROCSSValueList(false);
 
   const nsStyleBorder* border = StyleBorder();
   // Four slice numbers.
   NS_FOR_CSS_SIDES (side) {
     RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
-    SetValueToCoord(val, border->mBorderImageSlice.Get(side), true, nullptr);
+    SetValueToCoord(val, border->mBorderImageSlice.Get(side), true);
     valueList->AppendCSSValue(val.forget());
   }
 
   // Fill keyword.
   if (NS_STYLE_BORDER_IMAGE_SLICE_FILL == border->mBorderImageFill) {
     RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
     val->SetIdent(eCSSKeyword_fill);
     valueList->AppendCSSValue(val.forget());
@@ -4240,34 +4244,34 @@ nsComputedDOMStyle::DoGetBorderImageSlic
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetBorderImageWidth()
 {
   const nsStyleBorder* border = StyleBorder();
   RefPtr<nsDOMCSSValueList> valueList = GetROCSSValueList(false);
   NS_FOR_CSS_SIDES (side) {
     RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
     SetValueToCoord(val, border->mBorderImageWidth.Get(side),
-                    true, nullptr);
+                    true);
     valueList->AppendCSSValue(val.forget());
   }
 
   return valueList.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetBorderImageOutset()
 {
   RefPtr<nsDOMCSSValueList> valueList = GetROCSSValueList(false);
 
   const nsStyleBorder* border = StyleBorder();
   // four slice numbers
   NS_FOR_CSS_SIDES (side) {
     RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
     SetValueToCoord(val, border->mBorderImageOutset.Get(side),
-                    true, nullptr);
+                    true);
     valueList->AppendCSSValue(val.forget());
   }
 
   return valueList.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetBorderImageRepeat()
@@ -4304,17 +4308,17 @@ nsComputedDOMStyle::DoGetFlexBasis()
   //     if (my flex container is horizontal) {
   //       percentageBaseGetter = &nsComputedDOMStyle::GetCBContentWidth;
   //     } else {
   //       percentageBaseGetter = &nsComputedDOMStyle::GetCBContentHeight;
   //     }
   //   }
 
   SetValueToCoord(val, StylePosition()->mFlexBasis, true,
-                  nullptr, nsCSSProps::kWidthKTable);
+                  nullptr, nullptr, nsCSSProps::kWidthKTable);
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetFlexDirection()
 {
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
   val->SetIdent(
@@ -4786,17 +4790,17 @@ nsComputedDOMStyle::DoGetHeight()
       StyleCoordToNSCoord(positionData->mMinHeight,
                           &nsComputedDOMStyle::GetCBContentHeight, 0, true);
 
     nscoord maxHeight =
       StyleCoordToNSCoord(positionData->mMaxHeight,
                           &nsComputedDOMStyle::GetCBContentHeight,
                           nscoord_MAX, true);
 
-    SetValueToCoord(val, positionData->mHeight, true, nullptr,
+    SetValueToCoord(val, positionData->mHeight, true, nullptr, nullptr,
                     nsCSSProps::kWidthKTable, minHeight, maxHeight);
   }
 
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetWidth()
@@ -4830,38 +4834,38 @@ nsComputedDOMStyle::DoGetWidth()
       StyleCoordToNSCoord(positionData->mMinWidth,
                           &nsComputedDOMStyle::GetCBContentWidth, 0, true);
 
     nscoord maxWidth =
       StyleCoordToNSCoord(positionData->mMaxWidth,
                           &nsComputedDOMStyle::GetCBContentWidth,
                           nscoord_MAX, true);
 
-    SetValueToCoord(val, positionData->mWidth, true, nullptr,
+    SetValueToCoord(val, positionData->mWidth, true, nullptr, nullptr,
                     nsCSSProps::kWidthKTable, minWidth, maxWidth);
   }
 
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetMaxHeight()
 {
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
-  SetValueToCoord(val, StylePosition()->mMaxHeight, true,
+  SetValueToCoord(val, StylePosition()->mMaxHeight, true, this,
                   &nsComputedDOMStyle::GetCBContentHeight,
                   nsCSSProps::kWidthKTable);
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetMaxWidth()
 {
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
-  SetValueToCoord(val, StylePosition()->mMaxWidth, true,
+  SetValueToCoord(val, StylePosition()->mMaxWidth, true, this,
                   &nsComputedDOMStyle::GetCBContentWidth,
                   nsCSSProps::kWidthKTable);
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetMinHeight()
 {
@@ -4871,17 +4875,17 @@ nsComputedDOMStyle::DoGetMinHeight()
   if (eStyleUnit_Auto == minHeight.GetUnit()) {
     // In non-flexbox contexts, "min-height: auto" means "min-height: 0"
     // XXXdholbert For flex items, we should set |minHeight| to the
     // -moz-min-content keyword, instead of 0, once we support -moz-min-content
     // as a height value.
     minHeight.SetCoordValue(0);
   }
 
-  SetValueToCoord(val, minHeight, true,
+  SetValueToCoord(val, minHeight, true, this,
                   &nsComputedDOMStyle::GetCBContentHeight,
                   nsCSSProps::kWidthKTable);
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetMinWidth()
 {
@@ -4899,17 +4903,17 @@ nsComputedDOMStyle::DoGetMinWidth()
                  flexContainer->GetType() == nsGkAtoms::flexContainerFrame,
                  "IsFlexItem() lied...?");
 
       if (static_cast<nsFlexContainerFrame*>(flexContainer)->IsHorizontal()) {
         minWidth.SetIntValue(NS_STYLE_WIDTH_MIN_CONTENT, eStyleUnit_Enumerated);
       }
     }
   }
-  SetValueToCoord(val, minWidth, true,
+  SetValueToCoord(val, minWidth, true, this,
                   &nsComputedDOMStyle::GetCBContentWidth,
                   nsCSSProps::kWidthKTable);
   return val.forget();
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetMixBlendMode()
 {
@@ -4958,17 +4962,17 @@ nsComputedDOMStyle::DoGetRight()
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::DoGetTop()
 {
   return GetOffsetWidthFor(NS_SIDE_TOP);
 }
 
-nsDOMCSSValueList*
+/* static */ nsDOMCSSValueList*
 nsComputedDOMStyle::GetROCSSValueList(bool aCommaDelimited)
 {
   return new nsDOMCSSValueList(aCommaDelimited, true);
 }
 
 already_AddRefed<CSSValue>
 nsComputedDOMStyle::GetOffsetWidthFor(mozilla::css::Side aSide)
 {
@@ -5271,41 +5275,47 @@ nsComputedDOMStyle::GetBorderStyleFor(mo
 {
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
   val->SetIdent(
     nsCSSProps::ValueToKeywordEnum(StyleBorder()->GetBorderStyle(aSide),
                                    nsCSSProps::kBorderStyleKTable));
   return val.forget();
 }
 
-void
+/* static */ void
 nsComputedDOMStyle::SetValueToCoord(nsROCSSPrimitiveValue* aValue,
                                     const nsStyleCoord& aCoord,
                                     bool aClampNegativeCalc,
+                                    nsComputedDOMStyle*
+                                      aPercentageBaseGetterThis,
                                     PercentageBaseGetter aPercentageBaseGetter,
                                     const KTableEntry aTable[],
                                     nscoord aMinAppUnits,
                                     nscoord aMaxAppUnits)
 {
   NS_PRECONDITION(aValue, "Must have a value to work with");
+  MOZ_ASSERT(!aPercentageBaseGetterThis == !aPercentageBaseGetter,
+             "Must either have both aPercentageBaseGetterThis and "
+             "aPercentageBaseGetter or neither.");
 
   switch (aCoord.GetUnit()) {
     case eStyleUnit_Normal:
       aValue->SetIdent(eCSSKeyword_normal);
       break;
 
     case eStyleUnit_Auto:
       aValue->SetIdent(eCSSKeyword_auto);
       break;
 
     case eStyleUnit_Percent:
       {
         nscoord percentageBase;
         if (aPercentageBaseGetter &&
-            (this->*aPercentageBaseGetter)(percentageBase)) {
+            (aPercentageBaseGetterThis->*aPercentageBaseGetter)(percentageBase))
+        {
           nscoord val = NSCoordSaturatingMultiply(percentageBase,
                                                   aCoord.GetPercentValue());
           aValue->SetAppUnits(std::max(aMinAppUnits, std::min(val, aMaxAppUnits)));
         } else {
           aValue->SetPercent(aCoord.GetPercentValue());
         }
       }
       break;
@@ -5341,17 +5351,18 @@ nsComputedDOMStyle::SetValueToCoord(nsRO
         nscoord val = nsRuleNode::ComputeCoordPercentCalc(aCoord, 0);
         if (aClampNegativeCalc && val < 0) {
           MOZ_ASSERT(aCoord.IsCalcUnit(),
                      "parser should have rejected value");
           val = 0;
         }
         aValue->SetAppUnits(std::max(aMinAppUnits, std::min(val, aMaxAppUnits)));
       } else if (aPercentageBaseGetter &&
-                 (this->*aPercentageBaseGetter)(percentageBase)) {
+                 (aPercentageBaseGetterThis->*aPercentageBaseGetter)
+                   (percentageBase)) {
         nscoord val =
           nsRuleNode::ComputeCoordPercentCalc(aCoord, percentageBase);
         if (aClampNegativeCalc && val < 0) {
           MOZ_ASSERT(aCoord.IsCalcUnit(),
                      "parser should have rejected value");
           val = 0;
         }
         aValue->SetAppUnits(std::max(aMinAppUnits, std::min(val, aMaxAppUnits)));
@@ -5955,17 +5966,17 @@ nsComputedDOMStyle::CreatePrimitiveValue
       const nsTArray<nsStyleCoord>& radii = aStyleBasicShape->Coordinates();
       MOZ_ASSERT(radii.Length() ==
                  (type == StyleBasicShapeType::Circle ? 1 : 2),
                  "wrong number of radii");
       for (size_t i = 0; i < radii.Length(); ++i) {
         nsAutoString radius;
         RefPtr<nsROCSSPrimitiveValue> value = new nsROCSSPrimitiveValue;
         bool clampNegativeCalc = true;
-        SetValueToCoord(value, radii[i], clampNegativeCalc, nullptr,
+        SetValueToCoord(value, radii[i], clampNegativeCalc, nullptr, nullptr,
                         nsCSSProps::kShapeRadiusKTable);
         value->GetCssText(radius);
         shapeFunctionString.Append(radius);
         shapeFunctionString.Append(' ');
       }
       shapeFunctionString.AppendLiteral("at ");
 
       RefPtr<nsDOMCSSValueList> position = GetROCSSValueList(false);

--- a/layout/style/nsComputedDOMStyle.h
+++ b/layout/style/nsComputedDOMStyle.h
@@ -16,16 +16,17 @@
 #include "nsCSSProps.h"
 #include "nsDOMCSSDeclaration.h"
 #include "nsStyleContext.h"
 #include "nsIWeakReferenceUtils.h"
 #include "mozilla/gfx/Types.h"
 #include "nsCoord.h"
 #include "nsColor.h"
 #include "nsIContent.h"
+#include "nsStyleImage.h"
 #include "nsStyleStruct.h"
 
 namespace mozilla {
 namespace dom {
 class Element;
 } // namespace dom
 struct ComputedGridTrackInfo;
 } // namespace mozilla
@@ -39,16 +40,21 @@ class nsROCSSPrimitiveValue;
 class nsStyleCoord;
 class nsStyleCorners;
 struct nsStyleFilter;
 class nsStyleGradient;
 struct nsStyleImage;
 class nsStyleSides;
 struct nsTimingFunction;
 
+namespace mozilla {
+void SetValueToStyleImage(const nsStyleImage& aStyleImage,
+                          nsROCSSPrimitiveValue* aValue);
+} // namespace mozilla
+
 class nsComputedDOMStyle final : public nsDOMCSSDeclaration
                                , public nsStubMutationObserver
 {
 private:
   // Convenience typedefs:
   typedef nsCSSProps::KTableEntry KTableEntry;
   typedef mozilla::dom::CSSValue CSSValue;
 
@@ -202,21 +208,28 @@ private:
                                                bool aIsBoxShadow);
 
   already_AddRefed<CSSValue> GetBackgroundList(
     uint8_t nsStyleImageLayers::Layer::* aMember,
     uint32_t nsStyleImageLayers::* aCount,
     const nsStyleImageLayers& aLayers,
     const KTableEntry aTable[]);
 
-  void GetCSSGradientString(const nsStyleGradient* aGradient,
-                            nsAString& aString);
-  void GetImageRectString(nsIURI* aURI,
-                          const nsStyleSides& aCropRect,
-                          nsString& aString);
+  // SetValueToStyleImage uses GetCSSGradientString and GetImageRectString. We
+  // would make it a private member function except that it's used by
+  // CSSComputedValue, which has a member function called by this class, and we
+  // can't forward-declare member functions.
+  friend void mozilla::SetValueToStyleImage(const nsStyleImage& aStyleImage,
+                                            nsROCSSPrimitiveValue* aValue);
+
+  static void GetCSSGradientString(const nsStyleGradient* aGradient,
+                                   nsAString& aString);
+  static void GetImageRectString(nsIURI* aURI,
+                                 const nsStyleSides& aCropRect,
+                                 nsString& aString);
   already_AddRefed<CSSValue> GetScrollSnapPoints(const nsStyleCoord& aCoord);
   void AppendTimingFunction(nsDOMCSSValueList *aValueList,
                             const nsTimingFunction& aTimingFunction);
 
   /* Properties queryable as CSSValues.
    * To avoid a name conflict with nsIDOM*CSS2Properties, these are all
    * DoGetXXX instead of GetXXX.
    */
@@ -574,57 +587,61 @@ private:
   already_AddRefed<CSSValue> DoGetClipPath();
   already_AddRefed<CSSValue> DoGetFilter();
   already_AddRefed<CSSValue> DoGetMaskType();
   already_AddRefed<CSSValue> DoGetPaintOrder();
 
   /* Custom properties */
   already_AddRefed<CSSValue> DoGetCustomProperty(const nsAString& aPropertyName);
 
-  nsDOMCSSValueList* GetROCSSValueList(bool aCommaDelimited);
+  static nsDOMCSSValueList* GetROCSSValueList(bool aCommaDelimited);
 
   /* Helper functions */
-  void SetToRGBAColor(nsROCSSPrimitiveValue* aValue, nscolor aColor);
-  void SetValueToStyleImage(const nsStyleImage& aStyleImage,
-                            nsROCSSPrimitiveValue* aValue);
+  static void SetToRGBAColor(nsROCSSPrimitiveValue* aValue, nscolor aColor);
   void SetValueToPositionCoord(
     const nsStyleImageLayers::Position::PositionCoord& aCoord,
     nsROCSSPrimitiveValue* aValue);
   void SetValueToPosition(const nsStyleImageLayers::Position& aPosition,
                           nsDOMCSSValueList* aValueList);
   void SetValueToFragmentOrURL(const FragmentOrURL* aFragmentOrURL,
                                nsROCSSPrimitiveValue* aValue);
 
   /**
    * A method to get a percentage base for a percentage value.  Returns true
    * if a percentage base value was determined, false otherwise.
    */
   typedef bool (nsComputedDOMStyle::*PercentageBaseGetter)(nscoord&);
 
   /**
    * Method to set aValue to aCoord.  If aCoord is a percentage value and
-   * aPercentageBaseGetter is not null, aPercentageBaseGetter is called.  If it
-   * returns true, the percentage base it outputs in its out param is used
-   * to compute an nscoord value.  If the getter is null or returns false,
-   * the percent value of aCoord is set as a percent value on aValue.  aTable,
-   * if not null, is the keyword table to handle eStyleUnit_Enumerated.  When
-   * calling SetAppUnits on aValue (for coord or percent values), the value
-   * passed in will be clamped to be no less than aMinAppUnits and no more than
-   * aMaxAppUnits.
+   * aPercentageBaseGetter is not null, aPercentageBaseGetter is called.
+   * If aPercentageBaseGetter is provided, you must also supply
+   * aPercentageBaseGetterThis, as the object to call aPercentageBaseGetter on.
+   * (We don't just use |this| because we want to call this method from static
+   * functions that don't supply aPercentageBaseGetter.)  If
+   * aPercentageBaseGetter returns true, the percentage base it outputs in its
+   * out param is used to compute an nscoord value.  If the getter is null or
+   * returns false, the percent value of aCoord is set as a percent value on
+   * aValue.  aTable, if not null, is the keyword table to handle
+   * eStyleUnit_Enumerated.  When calling SetAppUnits on aValue (for coord or
+   * percent values), the value passed in will be clamped to be no less than
+   * aMinAppUnits and no more than aMaxAppUnits.
    *
    * XXXbz should caller pass in some sort of bitfield indicating which units
    * can be expected or something?
    */
-  void SetValueToCoord(nsROCSSPrimitiveValue* aValue,
-                       const nsStyleCoord& aCoord,
-                       bool aClampNegativeCalc,
-                       PercentageBaseGetter aPercentageBaseGetter = nullptr,
-                       const KTableEntry aTable[] = nullptr,
-                       nscoord aMinAppUnits = nscoord_MIN,
-                       nscoord aMaxAppUnits = nscoord_MAX);
+  static void SetValueToCoord(nsROCSSPrimitiveValue* aValue,
+                              const nsStyleCoord& aCoord,
+                              bool aClampNegativeCalc,
+                              nsComputedDOMStyle* aPercentageBaseGetterThis =
+                                nullptr,
+                              PercentageBaseGetter aPercentageBaseGetter = nullptr,
+                              const KTableEntry aTable[] = nullptr,
+                              nscoord aMinAppUnits = nscoord_MIN,
+                              nscoord aMaxAppUnits = nscoord_MAX);
 
   /**
    * If aCoord is a eStyleUnit_Coord returns the nscoord.  If it's
    * eStyleUnit_Percent, attempts to resolve the percentage base and returns
    * the resulting nscoord.  If it's some other unit or a percentge base can't
    * be determined, returns aDefaultValue.
    */
   nscoord StyleCoordToNSCoord(const nsStyleCoord& aCoord,