--- a/xpcom/base/nsCycleCollector.cpp
+++ b/xpcom/base/nsCycleCollector.cpp
@@ -602,16 +602,24 @@ struct GCGraph
     nsTArray<WeakMapping> mWeakMaps;
     uint32_t mRootCount;
 
     GCGraph() : mRootCount(0) {
     }
     ~GCGraph() {
     }
 
+    void Clear()
+    {
+        mNodes.Clear();
+        mEdges.Clear();
+        mWeakMaps.Clear();
+        mRootCount = 0;
+    }
+
     void SizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
                              size_t *aNodesSize, size_t *aEdgesSize) const {
         *aNodesSize = mNodes.SizeOfExcludingThis(aMallocSizeOf);
         *aEdgesSize = mEdges.SizeOfExcludingThis(aMallocSizeOf);
 
         // These fields are deliberately not measured:
         // - mWeakMaps entries, because the pointers are non-owning
     }
@@ -984,24 +992,16 @@ private:
     void MarkRoots(GCGraphBuilder &aBuilder);
     void ScanRoots();
     void ScanWeakMaps();
 
     // returns whether anything was collected
     bool CollectWhite(nsICycleCollectorListener *aListener);
 
     void CleanupAfterCollection();
-
-    void ClearGraph()
-    {
-        mGraph.mNodes.Clear();
-        mGraph.mEdges.Clear();
-        mGraph.mWeakMaps.Clear();
-        mGraph.mRootCount = 0;
-    }
 };
 
 /**
  * GraphWalker is templatized over a Visitor class that must provide
  * the following two methods:
  *
  * bool ShouldVisitNode(PtrInfo const *pi);
  * void VisitNode(PtrInfo *pi);
@@ -2610,17 +2610,17 @@ nsCycleCollector::PrepareForCollection(n
     timeLog.Checkpoint("PrepareForCollection()");
 }
 
 void
 nsCycleCollector::CleanupAfterCollection()
 {
     mWhiteNodes->Clear();
     mWhiteNodes = nullptr;
-    ClearGraph();
+    mGraph.Clear();
     mCollectionInProgress = false;
 
 #ifdef XP_OS2
     // Now that the cycle collector has freed some memory, we can try to
     // force the C library to give back as much memory to the system as
     // possible.
     _heapmin();
 #endif