diff --git a/layout/base/PresShell.cpp b/layout/base/PresShell.cpp
index c946f0954ead..dace0bc7216b 100644
--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -466,7 +466,7 @@ struct nsCallbackEventRequest
 
 // ----------------------------------------------------------------------------
 #define ASSERT_REFLOW_SCHEDULED_STATE()                                       \
-  NS_ASSERTION(mReflowScheduled ==                                            \
+  NS_ASSERTION(ObservingLayoutFlushes() ==                                    \
                  GetPresContext()->RefreshDriver()->                          \
                    IsLayoutFlushObserver(this), "Unexpected state")
 
@@ -794,11 +794,12 @@ nsIPresShell::nsIPresShell()
     , mFrozen(false)
     , mIsFirstPaint(false)
     , mObservesMutationsForPrint(false)
-    , mReflowScheduled(false)
     , mSuppressInterruptibleReflows(false)
     , mScrollPositionClampingScrollPortSizeSet(false)
     , mNeedLayoutFlush(true)
     , mNeedStyleFlush(true)
+    , mObservingStyleFlushes(false)
+    , mObservingLayoutFlushes(false)
     , mNeedThrottledAnimationFlush(true)
     , mPresShellId(0)
     , mFontSizeInflationEmPerLine(0)
@@ -1827,7 +1828,7 @@ PresShell::Initialize(nscoord aWidth, nscoord aHeight)
     FrameNeedsReflow(rootFrame, nsIPresShell::eResize, NS_FRAME_IS_DIRTY);
     NS_ASSERTION(mDirtyRoots.Contains(rootFrame),
                  "Should be in mDirtyRoots now");
-    NS_ASSERTION(mReflowScheduled, "Why no reflow scheduled?");
+    NS_ASSERTION(mObservingLayoutFlushes, "Why no reflow scheduled?");
   }
 
   // Restore our root scroll position now if we're getting here after EndLoad
@@ -2864,9 +2865,9 @@ PresShell::CancelAllPendingReflows()
 {
   mDirtyRoots.Clear();
 
-  if (mReflowScheduled) {
+  if (mObservingLayoutFlushes) {
     GetPresContext()->RefreshDriver()->RemoveLayoutFlushObserver(this);
-    mReflowScheduled = false;
+    mObservingLayoutFlushes = false;
   }
 
   ASSERT_REFLOW_SCHEDULED_STATE();
@@ -9080,8 +9081,8 @@ void
 PresShell::MaybeScheduleReflow()
 {
   ASSERT_REFLOW_SCHEDULED_STATE();
-  if (mReflowScheduled || mIsDestroying || mIsReflowing ||
-      mDirtyRoots.Length() == 0)
+  if (mObservingLayoutFlushes || mIsDestroying || mIsReflowing ||
+      mDirtyRoots.IsEmpty())
     return;
 
   if (!mPresContext->HasPendingInterrupt() || !ScheduleReflowOffTimer()) {
@@ -9094,13 +9095,8 @@ PresShell::MaybeScheduleReflow()
 void
 PresShell::ScheduleReflow()
 {
-  NS_PRECONDITION(!mReflowScheduled, "Why are we trying to schedule a reflow?");
   ASSERT_REFLOW_SCHEDULED_STATE();
-
-  if (GetPresContext()->RefreshDriver()->AddLayoutFlushObserver(this)) {
-    mReflowScheduled = true;
-  }
-
+  DoObserveLayoutFlushes();
   ASSERT_REFLOW_SCHEDULED_STATE();
 }
 
@@ -9175,7 +9171,7 @@ PresShell::sReflowContinueCallback(nsITimer* aTimer, void* aPresShell)
 bool
 PresShell::ScheduleReflowOffTimer()
 {
-  NS_PRECONDITION(!mReflowScheduled, "Shouldn't get here");
+  NS_PRECONDITION(!mObservingLayoutFlushes, "Shouldn't get here");
   ASSERT_REFLOW_SCHEDULED_STATE();
 
   if (!mReflowContinueTimer) {
@@ -9732,6 +9728,22 @@ nsIPresShell::RemovePostRefreshObserver(nsAPostRefreshObserver* aObserver)
   return true;
 }
 
+void
+nsIPresShell::DoObserveStyleFlushes()
+{
+  MOZ_ASSERT(!ObservingStyleFlushes());
+  mObservingStyleFlushes =
+    mPresContext->RefreshDriver()->AddStyleFlushObserver(this);
+}
+
+void
+nsIPresShell::DoObserveLayoutFlushes()
+{
+  MOZ_ASSERT(!ObservingLayoutFlushes());
+  mObservingLayoutFlushes =
+    mPresContext->RefreshDriver()->AddLayoutFlushObserver(this);
+}
+
 //------------------------------------------------------
 // End of protected and private methods on the PresShell
 //------------------------------------------------------
diff --git a/layout/base/RestyleManager.cpp b/layout/base/RestyleManager.cpp
index 2287e609fa74..85a5c65fc6f2 100644
--- a/layout/base/RestyleManager.cpp
+++ b/layout/base/RestyleManager.cpp
@@ -18,7 +18,6 @@ RestyleManager::RestyleManager(StyleBackendType aType,
   , mRestyleGeneration(1)
   , mHoverGeneration(0)
   , mType(aType)
-  , mObservingRefreshDriver(false)
   , mInStyleRefresh(false)
 {
   MOZ_ASSERT(mPresContext);
@@ -503,9 +502,8 @@ RestyleManager::PostRestyleEventInternal(bool aForLazyConstruction)
   // add ourselves as a refresh observer until then.
   bool inRefresh = !aForLazyConstruction && mInStyleRefresh;
   nsIPresShell* presShell = PresContext()->PresShell();
-  if (!ObservingRefreshDriver() && !inRefresh) {
-    SetObservingRefreshDriver(PresContext()->RefreshDriver()->
-        AddStyleFlushObserver(presShell));
+  if (!inRefresh) {
+    presShell->ObserveStyleFlushes();
   }
 
   // Unconditionally flag our document as needing a flush.  The other
diff --git a/layout/base/RestyleManager.h b/layout/base/RestyleManager.h
index 39e06efd2435..ae08b8220567 100644
--- a/layout/base/RestyleManager.h
+++ b/layout/base/RestyleManager.h
@@ -44,12 +44,6 @@ public:
   // as a result of a change to the :hover content state.
   uint32_t GetHoverGeneration() const { return mHoverGeneration; }
 
-  bool ObservingRefreshDriver() const { return mObservingRefreshDriver; }
-
-  void SetObservingRefreshDriver(bool aObserving) {
-      mObservingRefreshDriver = aObserving;
-  }
-
   void Disconnect() { mPresContext = nullptr; }
 
   static nsCString RestyleHintToString(nsRestyleHint aHint);
@@ -235,9 +229,6 @@ private:
 
   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;
diff --git a/layout/base/nsIPresShell.h b/layout/base/nsIPresShell.h
index 777713f7d4ba..5f44b3029a41 100644
--- a/layout/base/nsIPresShell.h
+++ b/layout/base/nsIPresShell.h
@@ -643,7 +643,16 @@ public:
   inline void SetNeedLayoutFlush();
   inline void SetNeedThrottledAnimationFlush();
 
-  bool NeedStyleFlush() { return mNeedStyleFlush; }
+  bool ObservingStyleFlushes() const { return mObservingStyleFlushes; }
+  bool ObservingLayoutFlushes() const { return mObservingLayoutFlushes; }
+
+  void ObserveStyleFlushes()
+  {
+    if (!ObservingStyleFlushes())
+      DoObserveStyleFlushes();
+  }
+
+  bool NeedStyleFlush() const { return mNeedStyleFlush; }
 
   /**
    * Callbacks will be called even if reflow itself fails for
@@ -1701,6 +1710,9 @@ protected:
   bool RemoveRefreshObserverInternal(nsARefreshObserver* aObserver,
                                      mozilla::FlushType aFlushType);
 
+  void DoObserveStyleFlushes();
+  void DoObserveLayoutFlushes();
+
   /**
    * Do computations necessary to determine if font size inflation is enabled.
    * This value is cached after computation, as the computation is somewhat
@@ -1791,7 +1803,7 @@ public:
   }
 
   bool HasPendingReflow() const
-    { return mReflowScheduled || mReflowContinueTimer; }
+    { return mObservingLayoutFlushes || mReflowContinueTimer; }
 
   void SyncWindowProperties(nsView* aView);
 
@@ -1888,10 +1900,6 @@ protected:
   bool                      mIsFirstPaint : 1;
   bool                      mObservesMutationsForPrint : 1;
 
-  // If true, we have a reflow scheduled. Guaranteed to be false if
-  // mReflowContinueTimer is non-null.
-  bool                      mReflowScheduled : 1;
-
   bool                      mSuppressInterruptibleReflows : 1;
   bool                      mScrollPositionClampingScrollPortSizeSet : 1;
 
@@ -1901,6 +1909,15 @@ protected:
   // True if a style flush might not be a no-op
   bool mNeedStyleFlush : 1;
 
+  // True if we're observing the refresh driver for style flushes.
+  bool mObservingStyleFlushes: 1;
+
+  // True if we're observing the refresh driver for layout flushes, that is, if
+  // we have a reflow scheduled.
+  //
+  // Guaranteed to be false if mReflowContinueTimer is non-null.
+  bool mObservingLayoutFlushes: 1;
+
   // True if there are throttled animations that would be processed when
   // performing a flush with mFlushAnimations == true.
   bool mNeedThrottledAnimationFlush : 1;
diff --git a/layout/base/nsRefreshDriver.cpp b/layout/base/nsRefreshDriver.cpp
index c57686a3cc25..c4deb3b286f9 100644
--- a/layout/base/nsRefreshDriver.cpp
+++ b/layout/base/nsRefreshDriver.cpp
@@ -1868,9 +1868,7 @@ nsRefreshDriver::Tick(int64_t aNowEpoch, TimeStamp aNowTime)
           }
 
           nsCOMPtr<nsIPresShell> shellKungFuDeathGrip(shell);
-          RestyleManager* restyleManager =
-            shell->GetPresContext()->RestyleManager();
-          restyleManager->SetObservingRefreshDriver(false);
+          shell->mObservingStyleFlushes = false;
           shell->FlushPendingNotifications(ChangesToFlush(FlushType::Style, false));
           // Inform the FontFaceSet that we ticked, so that it can resolve its
           // ready promise if it needs to (though it might still be waiting on
@@ -1901,7 +1899,7 @@ nsRefreshDriver::Tick(int64_t aNowEpoch, TimeStamp aNowTime)
         }
 
         nsCOMPtr<nsIPresShell> shellKungFuDeathGrip(shell);
-        shell->mReflowScheduled = false;
+        shell->mObservingLayoutFlushes = false;
         shell->mSuppressInterruptibleReflows = false;
         FlushType flushType = HasPendingAnimations(shell)
                                ? FlushType::Layout