--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -13139,27 +13139,23 @@ nsIDocument::UpdateStyleBackendType()
 {
   MOZ_ASSERT(mStyleBackendType == StyleBackendType::None,
              "no need to call UpdateStyleBackendType now");
 
   // Assume Gecko by default.
   mStyleBackendType = StyleBackendType::Gecko;
 
 #ifdef MOZ_STYLO
-  // XXX For now we use a Servo-backed style set only for (X)HTML documents
-  // in content docshells.  This should let us avoid implementing XUL-specific
-  // CSS features.  And apart from not supporting SVG properties in Servo
-  // yet, the root SVG element likes to create a style sheet for an SVG
-  // document before we have a pres shell (i.e. before we make the decision
-  // here about whether to use a Gecko- or Servo-backed style system), so
-  // we avoid Servo-backed style sets for SVG documents.
-  if (!mDocumentContainer) {
-    NS_WARNING("stylo: No docshell yet, assuming Gecko style system");
-  } else if (nsLayoutUtils::SupportsServoStyleBackend(this)) {
-    mStyleBackendType = StyleBackendType::Servo;
+  if (nsLayoutUtils::StyloEnabled()) {
+    if (!mDocumentContainer) {
+      NS_WARNING("stylo: No docshell yet, assuming Gecko style system");
+    } else if ((IsHTMLOrXHTML() || IsSVGDocument()) &&
+               IsContentDocument()) {
+      mStyleBackendType = StyleBackendType::Servo;
+    }
   }
 #endif
 }
 
 /**
  * Helper function for |nsDocument::PrincipalFlashClassification|
  *
  * Adds a table name string to a table list (a comma separated string). The

--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -9336,25 +9336,16 @@ nsLayoutUtils::ComputePartialPrerenderAr
   // redistributing from one axis to another, or from one side to another.
   nscoord xExcess = aPrerenderSize.width - aDirtyRect.width;
   nscoord yExcess = aPrerenderSize.height - aDirtyRect.height;
   nsRect result = aDirtyRect;
   result.Inflate(xExcess / 2, yExcess / 2);
   return result.MoveInsideAndClamp(aOverflow);
 }
 
-
-/* static */ bool
-nsLayoutUtils::SupportsServoStyleBackend(nsIDocument* aDocument)
-{
-  return StyloEnabled() &&
-         (aDocument->IsHTMLOrXHTML() || aDocument->IsSVGDocument()) &&
-         aDocument->IsContentDocument();
-}
-
 static
 bool
 LineHasNonEmptyContentWorker(nsIFrame* aFrame)
 {
   // Look for non-empty frames, but ignore inline and br frames.
   // For inline frames, descend into the children, if any.
   if (aFrame->IsInlineFrame()) {
     for (nsIFrame* child : aFrame->PrincipalChildList()) {

--- a/layout/base/nsLayoutUtils.h
+++ b/layout/base/nsLayoutUtils.h
@@ -2908,24 +2908,16 @@ public:
    * @return A rectangle that includes |aDirtyRect|, is clamped to |aOverflow|,
    *         and is no larger than |aPrerenderSize|.
    */
   static nsRect ComputePartialPrerenderArea(const nsRect& aDirtyRect,
                                             const nsRect& aOverflow,
                                             const nsSize& aPrerenderSize);
 
   /*
-   * Returns whether the given document supports being rendered with a
-   * Servo-backed style system.  This checks whether Stylo is enabled
-   * globally, that the document is an HTML document, and that it is
-   * being presented in a content docshell.
-   */
-  static bool SupportsServoStyleBackend(nsIDocument* aDocument);
-
-  /*
    * Checks whether a node is an invisible break.
    * If not, returns the first frame on the next line if such a next line exists.
    *
    * @return  true if the node is an invisible break.
    *          aNextLineFrame is returned null in this case.
    *          false if the node causes a visible break or if the node is no break.
    *
    * @param   aNextLineFrame  assigned to first frame on the next line if such a