--- a/gfx/layers/ipc/CompositorBridgeParent.cpp
+++ b/gfx/layers/ipc/CompositorBridgeParent.cpp
@@ -1706,16 +1706,22 @@ CompositorBridgeParent::DeallocPWebRende
 }
 
 RefPtr<WebRenderBridgeParent>
 CompositorBridgeParent::GetWebRenderBridgeParent() const
 {
   return mWrBridge;
 }
 
+Maybe<TimeStamp>
+CompositorBridgeParent::GetTestingTimeStamp() const
+{
+  return mIsTesting ? Some(mTestTime) : Nothing();
+}
+
 void
 CompositorBridgeParent::SetWebRenderProfilerEnabled(bool aEnabled)
 {
   MonitorAutoLock lock(*sIndirectLayerTreesLock);
   for (auto it = sIndirectLayerTrees.begin(); it != sIndirectLayerTrees.end(); it++) {
     LayerTreeState* state = &it->second;
     if (state->mWrBridge) {
       state->mWrBridge->SetWebRenderProfilerEnabled(aEnabled);

--- a/gfx/layers/ipc/CompositorBridgeParent.h
+++ b/gfx/layers/ipc/CompositorBridgeParent.h
@@ -452,16 +452,17 @@ public:
   }
 
   PWebRenderBridgeParent* AllocPWebRenderBridgeParent(const wr::PipelineId& aPipelineId,
                                                       const LayoutDeviceIntSize& aSize,
                                                       TextureFactoryIdentifier* aTextureFactoryIdentifier,
                                                       uint32_t* aIdNamespace) override;
   bool DeallocPWebRenderBridgeParent(PWebRenderBridgeParent* aActor) override;
   RefPtr<WebRenderBridgeParent> GetWebRenderBridgeParent() const;
+  Maybe<TimeStamp> GetTestingTimeStamp() const;
 
   static void SetWebRenderProfilerEnabled(bool aEnabled);
 
   static CompositorBridgeParent* GetCompositorBridgeParentFromLayersId(const uint64_t& aLayersId);
 
 #if defined(MOZ_WIDGET_ANDROID)
   gfx::IntSize GetEGLSurfaceSize() {
     return mEGLSurfaceSize;

--- a/gfx/layers/wr/WebRenderBridgeParent.cpp
+++ b/gfx/layers/wr/WebRenderBridgeParent.cpp
@@ -401,17 +401,18 @@ WebRenderBridgeParent::UpdateAPZ()
 bool
 WebRenderBridgeParent::PushAPZStateToWR(nsTArray<WrTransformProperty>& aTransformArray)
 {
   CompositorBridgeParent* cbp = GetRootCompositorBridgeParent();
   if (!cbp) {
     return false;
   }
   if (RefPtr<APZCTreeManager> apzc = cbp->GetAPZCTreeManager()) {
-    TimeStamp animationTime = mCompositorScheduler->GetLastComposeTime();
+    TimeStamp animationTime = cbp->GetTestingTimeStamp().valueOr(
+        mCompositorScheduler->GetLastComposeTime());
     TimeDuration frameInterval = cbp->GetVsyncInterval();
     // As with the non-webrender codepath in AsyncCompositionManager, we want to
     // use the timestamp for the next vsync when advancing animations.
     if (frameInterval != TimeDuration::Forever()) {
       animationTime += frameInterval;
     }
     return apzc->PushStateToWR(mApi, animationTime, aTransformArray);
   }
@@ -834,22 +835,30 @@ WebRenderBridgeParent::RecvGetAPZTestDat
 
 void
 WebRenderBridgeParent::ActorDestroy(ActorDestroyReason aWhy)
 {
   Destroy();
 }
 
 void
+WebRenderBridgeParent::AdvanceAnimations()
+{
+  TimeStamp animTime = mCompositorScheduler->GetLastComposeTime();
+  if (CompositorBridgeParent* cbp = GetRootCompositorBridgeParent()) {
+    animTime = cbp->GetTestingTimeStamp().valueOr(animTime);
+  }
+  AnimationHelper::SampleAnimations(mAnimStorage, animTime);
+}
+
+void
 WebRenderBridgeParent::SampleAnimations(nsTArray<WrOpacityProperty>& aOpacityArray,
                                         nsTArray<WrTransformProperty>& aTransformArray)
 {
-  AnimationHelper::SampleAnimations(mAnimStorage,
-                                    mCompositorScheduler->
-                                      GetLastComposeTime());
+  AdvanceAnimations();
 
   // return the animated data if has
   if (mAnimStorage->AnimatedValueCount()) {
     for(auto iter = mAnimStorage->ConstAnimatedValueTableIter();
         !iter.Done(); iter.Next()) {
       AnimatedValue * value = iter.UserData();
       if (value->mType == AnimatedValue::TRANSFORM) {
         aTransformArray.AppendElement(

--- a/gfx/layers/wr/WebRenderBridgeParent.h
+++ b/gfx/layers/wr/WebRenderBridgeParent.h
@@ -209,16 +209,17 @@ private:
                    InfallibleTArray<OpDestroy>&& aToDestroy,
                    const uint64_t& aFwdTransactionId,
                    const uint64_t& aTransactionId,
                    const WrSize& aContentSize,
                    const ByteBuffer& dl,
                    const WrBuiltDisplayListDescriptor& dlDesc,
                    const WebRenderScrollData& aScrollData);
 
+  void AdvanceAnimations();
   void SampleAnimations(nsTArray<WrOpacityProperty>& aOpacityArray,
                         nsTArray<WrTransformProperty>& aTransformArray);
 
   CompositorBridgeParent* GetRootCompositorBridgeParent() const;
 
   // Have APZ push the async scroll state to WR. Returns true if an APZ
   // animation is in effect and we need to schedule another composition.
   // If scrollbars need their transforms updated, the provided aTransformArray