--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -61,16 +61,23 @@ EqualURIs(nsIURI *aURI1, nsIURI *aURI2)
 
 static bool
 EqualURIs(mozilla::css::URLValue *aURI1, mozilla::css::URLValue *aURI2)
 {
   return aURI1 == aURI2 ||    // handle null==null, and optimize
          (aURI1 && aURI2 && aURI1->URIEquals(*aURI2));
 }
 
+static
+bool EqualURIs(const FragmentOrURL* aURI1, const FragmentOrURL* aURI2)
+{
+  return aURI1 == aURI2 ||    // handle null==null, and optimize
+         (aURI1 && aURI2 && *aURI1 == *aURI2);
+}
+
 static bool
 EqualImages(imgIRequest *aImage1, imgIRequest* aImage2)
 {
   if (aImage1 == aImage2) {
     return true;
   }
 
   if (!aImage1 || !aImage2) {
@@ -999,16 +1006,113 @@ nsStyleBasicShape::GetShapeTypeName() co
     case nsStyleBasicShape::Type::eInset:
       return eCSSKeyword_inset;
   }
   NS_NOTREACHED("unexpected type");
   return eCSSKeyword_UNKNOWN;
 }
 
 // --------------------
+// FragmentOrURL
+//
+
+void
+FragmentOrURL::SetValue(const nsCSSValue* aValue)
+{
+  mozilla::css::URLValue *urlVal = aValue->GetURLStructValue();
+  MOZ_ASSERT_IF(urlVal->GetLocalURLFlag(), urlVal->GetURI());
+  mIsLocalRef = urlVal->GetLocalURLFlag();
+
+  mURL = urlVal->GetURI();
+
+#ifdef DEBUG
+  if (mIsLocalRef) {
+    bool hasRef = false;
+    mURL->GetHasRef(&hasRef);
+    MOZ_ASSERT(hasRef);
+  }
+#endif
+}
+
+void
+FragmentOrURL::SetNull()
+{
+  mURL = nullptr;
+  mIsLocalRef = false;
+}
+
+FragmentOrURL&
+FragmentOrURL::operator=(const FragmentOrURL& aOther)
+{
+  mIsLocalRef = aOther.mIsLocalRef;
+  mURL = aOther.mURL;
+
+  return *this;
+}
+
+bool
+FragmentOrURL::operator==(const FragmentOrURL& aOther) const
+{
+  if (aOther.mIsLocalRef != mIsLocalRef) {
+    return false;
+  }
+
+  return EqualURIs(aOther.mURL, mURL);
+}
+
+bool
+FragmentOrURL::EqualsExceptRef(nsIURI* aURI) const
+{
+  bool ret = false;
+  mURL->EqualsExceptRef(aURI, &ret);
+  return ret;
+}
+
+void
+FragmentOrURL::GetSourceString(nsString &aRef) const
+{
+  MOZ_ASSERT(mURL);
+
+  nsCString cref;
+  if (mIsLocalRef) {
+    mURL->GetRef(cref);
+    cref.Insert('#', 0);
+  } else {
+    mURL->GetSpec(cref);
+  }
+
+  aRef = NS_ConvertUTF8toUTF16(cref);
+}
+
+already_AddRefed<nsIURI>
+FragmentOrURL::Resolve(nsIURI* aURI) const
+{
+  nsCOMPtr<nsIURI> result;
+
+  if (mIsLocalRef) {
+    nsCString ref;
+    mURL->GetRef(ref);
+
+    aURI->Clone(getter_AddRefs(result));
+    result->SetRef(ref);
+  } else {
+    result = mURL;
+  }
+
+  return result.forget();
+}
+
+already_AddRefed<nsIURI>
+FragmentOrURL::Resolve(nsIContent* aContent) const
+{
+  nsCOMPtr<nsIURI> url = aContent->GetBaseURI();
+  return Resolve(url);
+}
+
+// --------------------
 // nsStyleClipPath
 //
 nsStyleClipPath::nsStyleClipPath()
   : mURL(nullptr)
   , mType(StyleClipPathType::None_)
   , mSizingBox(StyleClipShapeSizing::NoBox)
 {
 }

--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -3204,16 +3204,49 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsSt
     return (IsVisibleBorderStyle(mColumnRuleStyle) ? mColumnRuleWidth : 0);
   }
 
 protected:
   nscoord mColumnRuleWidth;  // [reset] coord
   nscoord mTwipsPerPixel;
 };
 
+struct FragmentOrURL
+{
+  FragmentOrURL() : mIsLocalRef(false) {}
+  FragmentOrURL(const FragmentOrURL& aSource)
+    : mIsLocalRef(false)
+  { *this = aSource; }
+
+  void SetValue(const nsCSSValue* aValue);
+  void SetNull();
+
+  FragmentOrURL& operator=(const FragmentOrURL& aOther);
+  bool operator==(const FragmentOrURL& aOther) const;
+  bool operator!=(const FragmentOrURL& aOther) const {
+    return !(*this == aOther);
+  }
+
+  bool EqualsExceptRef(nsIURI* aURI) const;
+
+  nsIURI* GetSourceURL() const { return mURL; }
+  void GetSourceString(nsString& aRef) const;
+
+  // When matching a url with mIsLocalRef set, resolve it against aURI;
+  // Otherwise, ignore aURL and return mURL directly.
+  already_AddRefed<nsIURI> Resolve(nsIURI* aURI) const;
+  already_AddRefed<nsIURI> Resolve(nsIContent* aContent) const;
+
+  bool IsLocalRef() const { return mIsLocalRef; }
+
+private:
+  nsCOMPtr<nsIURI> mURL;
+  bool    mIsLocalRef;
+};
+
 enum nsStyleSVGPaintType {
   eStyleSVGPaintType_None = 1,
   eStyleSVGPaintType_Color,
   eStyleSVGPaintType_Server,
   eStyleSVGPaintType_ContextFill,
   eStyleSVGPaintType_ContextStroke
 };