diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index 4a8e8bd31e9f..d6f6e129771f 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -173,6 +173,7 @@ static uint32_t sPendingLoadCount;
 static bool sLoadingInProgress;
 
 static uint32_t sCCollectedWaitingForGC;
+static uint32_t sCCollectedZonesWaitingForGC;
 static uint32_t sLikelyShortLivingObjectsNeedingGC;
 static bool sPostGCEventsToConsole;
 static bool sPostGCEventsToObserver;
@@ -246,6 +247,7 @@ static bool
 NeedsGCAfterCC()
 {
   return sCCollectedWaitingForGC > 250 ||
+    sCCollectedZonesWaitingForGC > 0 ||
     sLikelyShortLivingObjectsNeedingGC > 2500 ||
     sNeedsGCAfterCC;
 }
@@ -1806,7 +1808,8 @@ nsJSContext::EndCycleCollectionCallback(CycleCollectorResults &aResults)
   // CCs, this won't happen.
   gCCStats.FinishCycleCollectionSlice();
 
-  sCCollectedWaitingForGC += aResults.mFreedRefCounted + aResults.mFreedGCed;
+  sCCollectedWaitingForGC += aResults.mFreedGCed;
+  sCCollectedZonesWaitingForGC += aResults.mFreedJSZones;
 
   TimeStamp endCCTimeStamp = TimeStamp::Now();
   uint32_t ccNowDuration = TimeBetween(gCCStats.mBeginTime, endCCTimeStamp);
@@ -1855,7 +1858,7 @@ nsJSContext::EndCycleCollectionCallback(CycleCollectorResults &aResults)
     }
 
     NS_NAMED_MULTILINE_LITERAL_STRING(kFmt,
-      MOZ_UTF16("CC(T+%.1f) max pause: %lums, total time: %lums, slices: %lu, suspected: %lu, visited: %lu RCed and %lu%s GCed, collected: %lu RCed and %lu GCed (%lu|%lu waiting for GC)%s\n")
+      MOZ_UTF16("CC(T+%.1f) max pause: %lums, total time: %lums, slices: %lu, suspected: %lu, visited: %lu RCed and %lu%s GCed, collected: %lu RCed and %lu GCed (%lu|%lu|%lu waiting for GC)%s\n")
       MOZ_UTF16("ForgetSkippable %lu times before CC, min: %lu ms, max: %lu ms, avg: %lu ms, total: %lu ms, max sync: %lu ms, removed: %lu"));
     nsString msg;
     msg.Adopt(nsTextFormatter::smprintf(kFmt.get(), double(delta) / PR_USEC_PER_SEC,
@@ -1863,7 +1866,7 @@ nsJSContext::EndCycleCollectionCallback(CycleCollectorResults &aResults)
                                         aResults.mNumSlices, gCCStats.mSuspected,
                                         aResults.mVisitedRefCounted, aResults.mVisitedGCed, mergeMsg.get(),
                                         aResults.mFreedRefCounted, aResults.mFreedGCed,
-                                        sCCollectedWaitingForGC, sLikelyShortLivingObjectsNeedingGC,
+                                        sCCollectedWaitingForGC, sCCollectedZonesWaitingForGC, sLikelyShortLivingObjectsNeedingGC,
                                         gcMsg.get(),
                                         sForgetSkippableBeforeCC,
                                         minForgetSkippableTime / PR_USEC_PER_MSEC,
@@ -1895,6 +1898,7 @@ nsJSContext::EndCycleCollectionCallback(CycleCollectorResults &aResults)
              MOZ_UTF16("\"RCed\": %lu, ")
              MOZ_UTF16("\"GCed\": %lu }, ")
          MOZ_UTF16("\"waiting_for_gc\": %lu, ")
+         MOZ_UTF16("\"zones_waiting_for_gc\": %lu, ")
          MOZ_UTF16("\"short_living_objects_waiting_for_gc\": %lu, ")
          MOZ_UTF16("\"forced_gc\": %d, ")
          MOZ_UTF16("\"forget_skippable\": { ")
@@ -1915,6 +1919,7 @@ nsJSContext::EndCycleCollectionCallback(CycleCollectorResults &aResults)
                                          aResults.mVisitedRefCounted, aResults.mVisitedGCed,
                                          aResults.mFreedRefCounted, aResults.mFreedGCed,
                                          sCCollectedWaitingForGC,
+                                         sCCollectedZonesWaitingForGC,
                                          sLikelyShortLivingObjectsNeedingGC,
                                          aResults.mForcedGC,
                                          sForgetSkippableBeforeCC,
@@ -2370,6 +2375,7 @@ DOMGCSliceCallback(JSRuntime *aRt, JS::GCProgress aProgress, const JS::GCDescrip
     nsJSContext::KillInterSliceGCTimer();
 
     sCCollectedWaitingForGC = 0;
+    sCCollectedZonesWaitingForGC = 0;
     sLikelyShortLivingObjectsNeedingGC = 0;
     sCleanupsSinceLastGC = 0;
     sNeedsFullCC = true;
@@ -2452,6 +2458,7 @@ mozilla::dom::StartupJSEnvironment()
   sPendingLoadCount = 0;
   sLoadingInProgress = false;
   sCCollectedWaitingForGC = 0;
+  sCCollectedZonesWaitingForGC = 0;
   sLikelyShortLivingObjectsNeedingGC = 0;
   sPostGCEventsToConsole = false;
   sNeedsFullCC = false;
diff --git a/xpcom/base/CycleCollectedJSRuntime.h b/xpcom/base/CycleCollectedJSRuntime.h
index 5ae7bf6f9d07..4685bf5c742b 100644
--- a/xpcom/base/CycleCollectedJSRuntime.h
+++ b/xpcom/base/CycleCollectedJSRuntime.h
@@ -93,6 +93,7 @@ struct CycleCollectorResults
     mVisitedGCed = 0;
     mFreedRefCounted = 0;
     mFreedGCed = 0;
+    mFreedJSZones = 0;
     mNumSlices = 1;
     // mNumSlices is initialized to one, because we call Init() after the
     // per-slice increment of mNumSlices has already occurred.
@@ -104,6 +105,7 @@ struct CycleCollectorResults
   uint32_t mVisitedGCed;
   uint32_t mFreedRefCounted;
   uint32_t mFreedGCed;
+  uint32_t mFreedJSZones;
   uint32_t mNumSlices;
 };
 
diff --git a/xpcom/base/nsCycleCollector.cpp b/xpcom/base/nsCycleCollector.cpp
index aecc0a265ff9..399b719758e5 100644
--- a/xpcom/base/nsCycleCollector.cpp
+++ b/xpcom/base/nsCycleCollector.cpp
@@ -3242,6 +3242,11 @@ nsCycleCollector::CollectWhite()
 
   whiteNodes.SetCapacity(mWhiteNodeCount);
   uint32_t numWhiteGCed = 0;
+  uint32_t numWhiteJSZones = 0;
+
+  bool hasJSRuntime = !!mJSRuntime;
+  nsCycleCollectionParticipant* zoneParticipant =
+    hasJSRuntime ? mJSRuntime->ZoneParticipant() : nullptr;
 
   NodePool::Enumerator etor(mGraph.mNodes);
   while (!etor.IsDone()) {
@@ -3251,6 +3256,9 @@ nsCycleCollector::CollectWhite()
       pinfo->mParticipant->Root(pinfo->mPointer);
       if (pinfo->IsGrayJS()) {
         ++numWhiteGCed;
+        if (MOZ_UNLIKELY(pinfo->mParticipant == zoneParticipant)) {
+          ++numWhiteJSZones;
+        }
       }
     }
   }
@@ -3260,6 +3268,7 @@ nsCycleCollector::CollectWhite()
              "More freed GCed nodes than total freed nodes.");
   mResults.mFreedRefCounted += count - numWhiteGCed;
   mResults.mFreedGCed += numWhiteGCed;
+  mResults.mFreedJSZones += numWhiteJSZones;
 
   timeLog.Checkpoint("CollectWhite::Root");