--- a/layout/base/GeckoRestyleManager.cpp
+++ b/layout/base/GeckoRestyleManager.cpp
@@ -79,17 +79,17 @@ ElementTagToString(dom::Element* aElemen
   nsCString result;
   nsDependentAtomString buf(aElement->NodeInfo()->NameAtom());
   result.AppendPrintf("(%s@%p)", NS_ConvertUTF16toUTF8(buf).get(), aElement);
   return result;
 }
 #endif
 
 GeckoRestyleManager::GeckoRestyleManager(nsPresContext* aPresContext)
-  : RestyleManager(aPresContext)
+  : RestyleManager(StyleBackendType::Gecko, aPresContext)
   , mDoRebuildAllStyleData(false)
   , mInRebuildAllStyleData(false)
   , mSkipAnimationRules(false)
   , mHavePendingNonAnimationRestyles(false)
   , mRebuildAllExtraHint(nsChangeHint(0))
   , mRebuildAllRestyleHint(nsRestyleHint(0))
   , mAnimationGeneration(0)
   , mReframingStyleContexts(nullptr)

--- a/layout/base/RestyleManager.cpp
+++ b/layout/base/RestyleManager.cpp
@@ -6,20 +6,22 @@
 
 #include "mozilla/RestyleManager.h"
 #include "mozilla/StyleSetHandleInlines.h"
 #include "nsIFrame.h"
 #include "nsIPresShellInlines.h"
 
 namespace mozilla {
 
-RestyleManager::RestyleManager(nsPresContext* aPresContext)
+RestyleManager::RestyleManager(StyleBackendType aType,
+                               nsPresContext* aPresContext)
   : mPresContext(aPresContext)
   , mRestyleGeneration(1)
   , mHoverGeneration(0)
+  , mType(aType)
   , mObservingRefreshDriver(false)
   , mInStyleRefresh(false)
 {
   MOZ_ASSERT(mPresContext);
 }
 
 /**
  * Calculates the change hint and the restyle hint for a given content state

--- a/layout/base/RestyleManager.h
+++ b/layout/base/RestyleManager.h
@@ -27,17 +27,17 @@ class Element;
 
 /**
  * Class for sharing data and logic common to both GeckoRestyleManager and
  * ServoRestyleManager.
  */
 class RestyleManager
 {
 protected:
-  explicit RestyleManager(nsPresContext* aPresContext);
+  RestyleManager(StyleBackendType aType, nsPresContext* aPresContext);
 
 public:
   typedef mozilla::dom::Element Element;
 
   // Get an integer that increments every time we process pending restyles.
   // The value is never 0.
   uint32_t GetRestyleGeneration() const { return mRestyleGeneration; }
 
@@ -171,32 +171,25 @@ protected:
     MOZ_ASSERT(mPresContext);
     return mPresContext;
   }
 
   nsCSSFrameConstructor* FrameConstructor() const {
     return PresContext()->FrameConstructor();
   }
 
-  inline bool IsGecko() const {
-    return !IsServo();
-  }
-
-  inline bool IsServo() const {
-#ifdef MOZ_STYLO
-    return PresContext()->StyleSet()->IsServo();
-#else
-    return false;
-#endif
-  }
+  MOZ_DECL_STYLO_METHODS(GeckoRestyleManager, ServoRestyleManager)
 
 private:
   nsPresContext* mPresContext; // weak, can be null after Disconnect().
   uint32_t mRestyleGeneration;
   uint32_t mHoverGeneration;
+
+  const StyleBackendType mType;
+
   // True if we're already waiting for a refresh notification.
   bool mObservingRefreshDriver;
 
 protected:
   // True if we're in the middle of a nsRefreshDriver refresh
   bool mInStyleRefresh;
 
   OverflowChangedTracker mOverflowChangedTracker;
@@ -224,13 +217,16 @@ protected:
    * style context should be passed.
    */
   static nsIFrame*
   GetNextContinuationWithSameStyle(nsIFrame* aFrame,
                                    nsStyleContext* aOldStyleContext,
                                    bool* aHaveMoreContinuations = nullptr);
 
   AnimationsWithDestroyedFrame* mAnimationsWithDestroyedFrame = nullptr;
+
+  friend class mozilla::GeckoRestyleManager;
+  friend class mozilla::ServoRestyleManager;
 };
 
 } // namespace mozilla
 
 #endif

--- a/layout/base/ServoRestyleManager.cpp
+++ b/layout/base/ServoRestyleManager.cpp
@@ -14,17 +14,17 @@
 #include "nsPrintfCString.h"
 #include "nsStyleChangeList.h"
 
 using namespace mozilla::dom;
 
 namespace mozilla {
 
 ServoRestyleManager::ServoRestyleManager(nsPresContext* aPresContext)
-  : RestyleManager(aPresContext)
+  : RestyleManager(StyleBackendType::Servo, aPresContext)
   , mReentrantChanges(nullptr)
 {
 }
 
 void
 ServoRestyleManager::PostRestyleEvent(Element* aElement,
                                       nsRestyleHint aRestyleHint,
                                       nsChangeHint aMinChangeHint)