--- a/gfx/layers/ipc/CompositorBridgeParent.cpp
+++ b/gfx/layers/ipc/CompositorBridgeParent.cpp
@@ -1329,19 +1329,20 @@ CompositorBridgeParent::FlushApzRepaints
   }
   RefPtr<CompositorBridgeParent> self = this;
   APZThreadUtils::RunOnControllerThread(NS_NewRunnableFunction([=] () {
     self->mApzcTreeManager->FlushApzRepaints(layersId);
   }));
 }
 
 void
-CompositorBridgeParent::GetAPZTestData(const LayerTransactionParent* aLayerTree,
+CompositorBridgeParent::GetAPZTestData(const uint64_t& aLayersId,
                                        APZTestData* aOutData)
 {
+  MOZ_ASSERT(aLayersId == mRootLayerTreeID);
   MonitorAutoLock lock(*sIndirectLayerTreesLock);
   *aOutData = sIndirectLayerTrees[mRootLayerTreeID].mApzTestData;
 }
 
 void
 CompositorBridgeParent::SetConfirmedTargetAPZC(const uint64_t& aLayersId,
                                                const uint64_t& aInputBlockId,
                                                const nsTArray<ScrollableLayerGuid>& aTargets)

--- a/gfx/layers/ipc/CompositorBridgeParent.h
+++ b/gfx/layers/ipc/CompositorBridgeParent.h
@@ -104,17 +104,17 @@ public:
 
   virtual void ForceComposite(LayerTransactionParent* aLayerTree) { }
   virtual bool SetTestSampleTime(LayerTransactionParent* aLayerTree,
                                  const TimeStamp& aTime) { return true; }
   virtual void LeaveTestMode(LayerTransactionParent* aLayerTree) { }
   virtual void ApplyAsyncProperties(LayerTransactionParent* aLayerTree) = 0;
   virtual CompositorAnimationStorage* GetAnimationStorage(const uint64_t& aId) { return nullptr; }
   virtual void FlushApzRepaints(const uint64_t& aLayersId) = 0;
-  virtual void GetAPZTestData(const LayerTransactionParent* aLayerTree,
+  virtual void GetAPZTestData(const uint64_t& aLayersId,
                               APZTestData* aOutData) { }
   virtual void SetConfirmedTargetAPZC(const uint64_t& aLayersId,
                                       const uint64_t& aInputBlockId,
                                       const nsTArray<ScrollableLayerGuid>& aTargets) = 0;
   virtual void UpdatePaintTime(LayerTransactionParent* aLayerTree, const TimeDuration& aPaintTime) {}
 
   virtual ShmemAllocator* AsShmemAllocator() override { return this; }
 
@@ -227,17 +227,17 @@ public:
   virtual void ForceComposite(LayerTransactionParent* aLayerTree) override;
   virtual bool SetTestSampleTime(LayerTransactionParent* aLayerTree,
                                  const TimeStamp& aTime) override;
   virtual void LeaveTestMode(LayerTransactionParent* aLayerTree) override;
   virtual void ApplyAsyncProperties(LayerTransactionParent* aLayerTree)
                override;
   virtual CompositorAnimationStorage* GetAnimationStorage(const uint64_t& aId) override;
   virtual void FlushApzRepaints(const uint64_t& aLayersId) override;
-  virtual void GetAPZTestData(const LayerTransactionParent* aLayerTree,
+  virtual void GetAPZTestData(const uint64_t& aLayersId,
                               APZTestData* aOutData) override;
   virtual void SetConfirmedTargetAPZC(const uint64_t& aLayersId,
                                       const uint64_t& aInputBlockId,
                                       const nsTArray<ScrollableLayerGuid>& aTargets) override;
   virtual AsyncCompositionManager* GetCompositionManager(LayerTransactionParent* aLayerTree) override { return mCompositionManager; }
 
   virtual PTextureParent* AllocPTextureParent(const SurfaceDescriptor& aSharedData,
                                               const LayersBackend& aLayersBackend,

--- a/gfx/layers/ipc/CrossProcessCompositorBridgeParent.cpp
+++ b/gfx/layers/ipc/CrossProcessCompositorBridgeParent.cpp
@@ -432,23 +432,22 @@ CrossProcessCompositorBridgeParent::Flus
   }
 
   MOZ_ASSERT(state->mParent);
   state->mParent->FlushApzRepaints(aLayersId);
 }
 
 void
 CrossProcessCompositorBridgeParent::GetAPZTestData(
-  const LayerTransactionParent* aLayerTree,
+  const uint64_t& aLayersId,
   APZTestData* aOutData)
 {
-  uint64_t id = aLayerTree->GetId();
-  MOZ_ASSERT(id != 0);
+  MOZ_ASSERT(aLayersId != 0);
   MonitorAutoLock lock(*sIndirectLayerTreesLock);
-  *aOutData = sIndirectLayerTrees[id].mApzTestData;
+  *aOutData = sIndirectLayerTrees[aLayersId].mApzTestData;
 }
 
 void
 CrossProcessCompositorBridgeParent::SetConfirmedTargetAPZC(
   const uint64_t& aLayersId,
   const uint64_t& aInputBlockId,
   const nsTArray<ScrollableLayerGuid>& aTargets)
 {

--- a/gfx/layers/ipc/CrossProcessCompositorBridgeParent.h
+++ b/gfx/layers/ipc/CrossProcessCompositorBridgeParent.h
@@ -100,17 +100,17 @@ public:
   virtual bool SetTestSampleTime(LayerTransactionParent* aLayerTree,
                                  const TimeStamp& aTime) override;
   virtual void LeaveTestMode(LayerTransactionParent* aLayerTree) override;
   virtual void ApplyAsyncProperties(LayerTransactionParent* aLayerTree)
                override;
   virtual CompositorAnimationStorage*
     GetAnimationStorage(const uint64_t& aId) override;
   virtual void FlushApzRepaints(const uint64_t& aLayersId) override;
-  virtual void GetAPZTestData(const LayerTransactionParent* aLayerTree,
+  virtual void GetAPZTestData(const uint64_t& aLayersId,
                               APZTestData* aOutData) override;
   virtual void SetConfirmedTargetAPZC(const uint64_t& aLayersId,
                                       const uint64_t& aInputBlockId,
                                       const nsTArray<ScrollableLayerGuid>& aTargets) override;
 
   virtual AsyncCompositionManager* GetCompositionManager(LayerTransactionParent* aParent) override;
   virtual mozilla::ipc::IPCResult RecvRemotePluginsReady()  override { return IPC_FAIL_NO_REASON(this); }
 

--- a/gfx/layers/ipc/LayerTransactionParent.cpp
+++ b/gfx/layers/ipc/LayerTransactionParent.cpp
@@ -844,17 +844,17 @@ LayerTransactionParent::RecvFlushApzRepa
 {
   mCompositorBridge->FlushApzRepaints(GetId());
   return IPC_OK();
 }
 
 mozilla::ipc::IPCResult
 LayerTransactionParent::RecvGetAPZTestData(APZTestData* aOutData)
 {
-  mCompositorBridge->GetAPZTestData(this, aOutData);
+  mCompositorBridge->GetAPZTestData(GetId(), aOutData);
   return IPC_OK();
 }
 
 mozilla::ipc::IPCResult
 LayerTransactionParent::RecvRequestProperty(const nsString& aProperty, float* aValue)
 {
   *aValue = -1;
   return IPC_OK();