--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -12241,26 +12241,22 @@ CSSParserImpl::ParseImageLayersItem(
   RefPtr<nsCSSValue::Array> positionXArr = nsCSSValue::Array::Create(2);
   RefPtr<nsCSSValue::Array> positionYArr = nsCSSValue::Array::Create(2);
   aState.mPositionX->mValue.SetArrayValue(positionXArr, eCSSUnit_Array);
   aState.mPositionY->mValue.SetArrayValue(positionYArr, eCSSUnit_Array);
 
   if (eCSSProperty_mask == aTable[nsStyleImageLayers::shorthand]) {
     aState.mOrigin->mValue.SetIntValue(NS_STYLE_IMAGELAYER_ORIGIN_BORDER,
                                        eCSSUnit_Enumerated);
-    aState.mRepeat->mXValue.SetIntValue(NS_STYLE_IMAGELAYER_REPEAT_NO_REPEAT,
-                                        eCSSUnit_Enumerated);
 
     positionXArr->Item(1).SetPercentValue(0.5f);
     positionYArr->Item(1).SetPercentValue(0.5f);
   } else {
     aState.mOrigin->mValue.SetIntValue(NS_STYLE_IMAGELAYER_ORIGIN_PADDING,
                                        eCSSUnit_Enumerated);
-    aState.mRepeat->mXValue.SetIntValue(NS_STYLE_IMAGELAYER_REPEAT_REPEAT,
-                                        eCSSUnit_Enumerated);
 
     positionXArr->Item(1).SetPercentValue(0.0f);
     positionYArr->Item(1).SetPercentValue(0.0f);
   }
 
   aState.mSize->mXValue.SetAutoValue();
   aState.mSize->mYValue.SetAutoValue();
   aState.mComposite->mValue.SetIntValue(NS_STYLE_MASK_COMPOSITE_ADD,

--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -6137,17 +6137,17 @@ nsComputedDOMStyle::DoGetMask()
   // a longhand.
   if (svg->mMask.mImageCount > 1 ||
       firstLayer.mClip != NS_STYLE_IMAGELAYER_CLIP_BORDER ||
       firstLayer.mOrigin != NS_STYLE_IMAGELAYER_ORIGIN_BORDER ||
       firstLayer.mComposite != NS_STYLE_MASK_COMPOSITE_ADD ||
       firstLayer.mMaskMode != NS_STYLE_MASK_MODE_MATCH_SOURCE ||
       !nsStyleImageLayers::IsInitialPositionForLayerType(
         firstLayer.mPosition, nsStyleImageLayers::LayerType::Mask) ||
-      !firstLayer.mRepeat.IsInitialValue(nsStyleImageLayers::LayerType::Mask) ||
+      !firstLayer.mRepeat.IsInitialValue() ||
       !firstLayer.mSize.IsInitialValue() ||
       !(firstLayer.mImage.GetType() == eStyleImageType_Null ||
         firstLayer.mImage.GetType() == eStyleImageType_Image)) {
     return nullptr;
   }
 
   RefPtr<nsROCSSPrimitiveValue> val = new nsROCSSPrimitiveValue;
 

--- a/layout/style/nsRuleNode.cpp
+++ b/layout/style/nsRuleNode.cpp
@@ -7254,17 +7254,17 @@ nsRuleNode::ComputeBackgroundData(void* 
                     parentBG->mImage.mLayers,
                     &nsStyleImageLayers::Layer::mImage,
                     initialImage, parentBG->mImage.mImageCount,
                     bg->mImage.mImageCount,
                     maxItemCount, rebuild, conditions);
 
   // background-repeat: enum, inherit, initial [pair list]
   nsStyleImageLayers::Repeat initialRepeat;
-  initialRepeat.SetInitialValues(nsStyleImageLayers::LayerType::Background);
+  initialRepeat.SetInitialValues();
   SetImageLayerPairList(aContext, *aRuleData->ValueForBackgroundRepeat(),
                         bg->mImage.mLayers,
                         parentBG->mImage.mLayers,
                         &nsStyleImageLayers::Layer::mRepeat,
                         initialRepeat, parentBG->mImage.mRepeatCount,
                         bg->mImage.mRepeatCount, maxItemCount, rebuild,
                         conditions);
 
@@ -9955,17 +9955,17 @@ nsRuleNode::ComputeSVGResetData(void* aS
                     &nsStyleImageLayers::Layer::mSourceURI,
                     RefPtr<css::URLValueData>(),
                     parentSVGReset->mMask.mImageCount,
                     svgReset->mMask.mImageCount,
                     maxItemCount, rebuild, conditions);
 
   // mask-repeat: enum, inherit, initial [pair list]
   nsStyleImageLayers::Repeat initialRepeat;
-  initialRepeat.SetInitialValues(nsStyleImageLayers::LayerType::Mask);
+  initialRepeat.SetInitialValues();
   SetImageLayerPairList(aContext, *aRuleData->ValueForMaskRepeat(),
                         svgReset->mMask.mLayers,
                         parentSVGReset->mMask.mLayers,
                         &nsStyleImageLayers::Layer::mRepeat,
                         initialRepeat, parentSVGReset->mMask.mRepeatCount,
                         svgReset->mMask.mRepeatCount, maxItemCount, rebuild,
                         conditions);
 

--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -2760,43 +2760,16 @@ nsStyleImageLayers::Size::operator==(con
              "bad mHeightType for aOther");
 
   return mWidthType == aOther.mWidthType &&
          mHeightType == aOther.mHeightType &&
          (mWidthType != eLengthPercentage || mWidth == aOther.mWidth) &&
          (mHeightType != eLengthPercentage || mHeight == aOther.mHeight);
 }
 
-bool
-nsStyleImageLayers::Repeat::IsInitialValue(LayerType aType) const
-{
-  if (aType == LayerType::Background) {
-    return mXRepeat == NS_STYLE_IMAGELAYER_REPEAT_REPEAT &&
-           mYRepeat == NS_STYLE_IMAGELAYER_REPEAT_REPEAT;
-  } else {
-    MOZ_ASSERT(aType == LayerType::Mask);
-    return mXRepeat == NS_STYLE_IMAGELAYER_REPEAT_NO_REPEAT &&
-           mYRepeat == NS_STYLE_IMAGELAYER_REPEAT_NO_REPEAT;
-  }
-}
-
-void
-nsStyleImageLayers::Repeat::SetInitialValues(LayerType aType)
-{
-  if (aType == LayerType::Background) {
-    mXRepeat = NS_STYLE_IMAGELAYER_REPEAT_REPEAT;
-    mYRepeat = NS_STYLE_IMAGELAYER_REPEAT_REPEAT;
-  } else {
-    MOZ_ASSERT(aType == LayerType::Mask);
-
-    mXRepeat = NS_STYLE_IMAGELAYER_REPEAT_NO_REPEAT;
-    mYRepeat = NS_STYLE_IMAGELAYER_REPEAT_NO_REPEAT;
-  }
-}
-
 nsStyleImageLayers::Layer::Layer()
   : mClip(NS_STYLE_IMAGELAYER_CLIP_BORDER)
   , mAttachment(NS_STYLE_IMAGELAYER_ATTACHMENT_SCROLL)
   , mBlendMode(NS_STYLE_BLEND_NORMAL)
   , mComposite(NS_STYLE_MASK_COMPOSITE_ADD)
   , mMaskMode(NS_STYLE_MASK_MODE_MATCH_SOURCE)
 {
   mImage.SetNull();
@@ -2805,17 +2778,17 @@ nsStyleImageLayers::Layer::Layer()
 
 nsStyleImageLayers::Layer::~Layer()
 {
 }
 
 void
 nsStyleImageLayers::Layer::Initialize(nsStyleImageLayers::LayerType aType)
 {
-  mRepeat.SetInitialValues(aType);
+  mRepeat.SetInitialValues();
 
   float initialPositionValue =
     nsStyleImageLayers::GetInitialPositionForLayerType(aType);
   mPosition.SetInitialPercentValues(initialPositionValue);
 
   if (aType == LayerType::Background) {
     mOrigin = NS_STYLE_IMAGELAYER_ORIGIN_PADDING;
   } else {

--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -740,25 +740,31 @@ struct nsStyleImageLayers {
   struct Repeat;
   friend struct Repeat;
   struct Repeat {
     uint8_t mXRepeat, mYRepeat;
 
     // Initialize nothing
     Repeat() {}
 
-    bool IsInitialValue(LayerType aType) const;
+    bool IsInitialValue() const {
+      return mXRepeat == NS_STYLE_IMAGELAYER_REPEAT_REPEAT &&
+             mYRepeat == NS_STYLE_IMAGELAYER_REPEAT_REPEAT;
+    }
 
     bool DependsOnPositioningAreaSize() const {
       return mXRepeat == NS_STYLE_IMAGELAYER_REPEAT_SPACE ||
              mYRepeat == NS_STYLE_IMAGELAYER_REPEAT_SPACE;
     }
 
     // Initialize to initial values
-    void SetInitialValues(LayerType aType);
+    void SetInitialValues() {
+      mXRepeat = NS_STYLE_IMAGELAYER_REPEAT_REPEAT;
+      mYRepeat = NS_STYLE_IMAGELAYER_REPEAT_REPEAT;
+    }
 
     bool operator==(const Repeat& aOther) const {
       return mXRepeat == aOther.mXRepeat &&
              mYRepeat == aOther.mYRepeat;
     }
     bool operator!=(const Repeat& aOther) const {
       return !(*this == aOther);
     }