diff --git a/layout/base/RestyleManager.cpp b/layout/base/RestyleManager.cpp
index 482b9612c181..759e06e4a622 100644
--- a/layout/base/RestyleManager.cpp
+++ b/layout/base/RestyleManager.cpp
@@ -1821,10 +1821,12 @@ RestyleManager::DebugVerifyStyleTree(nsIFrame* aFrame)
 
 // aContent must be the content for the frame in question, which may be
 // :before/:after content
-static void
-TryStartingTransition(nsPresContext *aPresContext, nsIContent *aContent,
-                      nsStyleContext *aOldStyleContext,
-                      nsRefPtr<nsStyleContext> *aNewStyleContext /* inout */)
+/* static */ void
+RestyleManager::TryStartingTransition(nsPresContext* aPresContext,
+                                      nsIContent* aContent,
+                                      nsStyleContext* aOldStyleContext,
+                                      nsRefPtr<nsStyleContext>*
+                                        aNewStyleContext /* inout */)
 {
   if (!aContent || !aContent->IsElement()) {
     return;
@@ -2608,8 +2610,8 @@ ElementRestyler::RestyleSelf(nsIFrame* aSelf, nsRestyleHint aRestyleHint)
 
   if (newContext != oldContext) {
     if (!copyFromContinuation) {
-      TryStartingTransition(mPresContext, aSelf->GetContent(),
-                            oldContext, &newContext);
+      RestyleManager::TryStartingTransition(mPresContext, aSelf->GetContent(),
+                                            oldContext, &newContext);
 
       CaptureChange(oldContext, newContext, assumeDifferenceHint);
     }
diff --git a/layout/base/RestyleManager.h b/layout/base/RestyleManager.h
index 6c3e60f9a681..516f1fbb1d71 100644
--- a/layout/base/RestyleManager.h
+++ b/layout/base/RestyleManager.h
@@ -176,6 +176,19 @@ public:
     return mReframingStyleContexts;
   }
 
+  /**
+   * Try starting a transition for an element or a ::before or ::after
+   * pseudo-element, given an old and new style context.  This may
+   * change the new style context if a transition is started.
+   *
+   * For the pseudo-elements, aContent must be the anonymous content
+   * that we're creating for that pseudo-element, not the real element.
+   */
+  static void
+  TryStartingTransition(nsPresContext* aPresContext, nsIContent* aContent,
+                        nsStyleContext* aOldStyleContext,
+                        nsRefPtr<nsStyleContext>* aNewStyleContext /* inout */);
+
 private:
   void RestyleForEmptyChange(Element* aContainer);