--- a/xpcom/base/nsCycleCollector.cpp
+++ b/xpcom/base/nsCycleCollector.cpp
@@ -976,26 +976,23 @@ private:
     void ShutdownCollect(nsICycleCollectorListener *aListener);
 
 public:
     bool Collect(ccType aCCType,
                  nsTArray<PtrInfo*> *aWhiteNodes,
                  nsCycleCollectorResults *aResults,
                  nsICycleCollectorListener *aListener);
 
-    // Prepare for and cleanup after one or more collection(s).
     bool PrepareForCollection(nsCycleCollectorResults *aResults,
                               nsTArray<PtrInfo*> *aWhiteNodes);
     void FixGrayBits(bool aForceGC);
     bool ShouldMergeZones(ccType aCCType);
     void CleanupAfterCollection();
 
-    // Start and finish an individual collection.
     void BeginCollection(ccType aCCType, nsICycleCollectorListener *aListener);
-    bool FinishCollection(nsICycleCollectorListener *aListener);
 
     bool FreeSnowWhite(bool aUntilNoSWInPurpleBuffer);
 
     uint32_t SuspectedCount();
     void Shutdown();
 
     void ClearGraph()
     {
@@ -2312,17 +2309,17 @@ nsCycleCollector::CollectWhite(nsICycleC
     //   - Root(whites), which should pin the whites in memory.
     //   - Unlink(whites), which drops outgoing links on each white.
     //   - Unroot(whites), which returns the whites to normal GC.
 
     nsresult rv;
     TimeLog timeLog;
 
     MOZ_ASSERT(mWhiteNodes->IsEmpty(),
-               "FinishCollection wasn't called?");
+               "CleanupAfterCollection wasn't called?");
 
     mWhiteNodes->SetCapacity(mWhiteNodeCount);
     uint32_t numWhiteGCed = 0;
 
     NodePool::Enumerator etor(mGraph.mNodes);
     while (!etor.IsDone())
     {
         PtrInfo *pinfo = etor.GetNext();
@@ -2628,17 +2625,19 @@ nsCycleCollector::PrepareForCollection(n
     timeLog.Checkpoint("PrepareForCollection()");
 
     return true;
 }
 
 void
 nsCycleCollector::CleanupAfterCollection()
 {
+    mWhiteNodes->Clear();
     mWhiteNodes = nullptr;
+    ClearGraph();
     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
@@ -2702,17 +2701,17 @@ nsCycleCollector::Collect(ccType aCCType
 
     FreeSnowWhite(true);
 
     if (aListener && NS_FAILED(aListener->Begin())) {
         aListener = nullptr;
     }
 
     BeginCollection(aCCType, aListener);
-    bool collectedAny = FinishCollection(aListener);
+    bool collectedAny = CollectWhite(aListener);
     CleanupAfterCollection();
     return collectedAny;
 }
 
 // Don't merge too many times in a row, and do at least a minimum
 // number of unmerged CCs in a row.
 static const uint32_t kMinConsecutiveUnmerged = 3;
 static const uint32_t kMaxConsecutiveMerged = 3;
@@ -2796,30 +2795,16 @@ nsCycleCollector::BeginCollection(ccType
                 }
             }
         }
     } else {
         mScanInProgress = false;
     }
 }
 
-bool
-nsCycleCollector::FinishCollection(nsICycleCollectorListener *aListener)
-{
-    TimeLog timeLog;
-    bool collected = CollectWhite(aListener);
-    timeLog.Checkpoint("CollectWhite()");
-
-    mWhiteNodes->Clear();
-    ClearGraph();
-    timeLog.Checkpoint("ClearGraph()");
-
-    return collected;
-}
-
 uint32_t
 nsCycleCollector::SuspectedCount()
 {
     CheckThreadSafety();
     return mPurpleBuf.Count();
 }
 
 void