--- a/gfx/layers/wr/WebRenderBridgeParent.cpp
+++ b/gfx/layers/wr/WebRenderBridgeParent.cpp
@@ -1160,34 +1160,42 @@ void
 WebRenderBridgeParent::ActorDestroy(ActorDestroyReason aWhy)
 {
   Destroy();
 }
 
 void
 WebRenderBridgeParent::AdvanceAnimations()
 {
-  Maybe<TimeStamp> testingTimeStamp;
   if (CompositorBridgeParent* cbp = GetRootCompositorBridgeParent()) {
-    testingTimeStamp = cbp->GetTestingTimeStamp();
+    Maybe<TimeStamp> testingTimeStamp = cbp->GetTestingTimeStamp();
+    if (testingTimeStamp) {
+      // If we are on testing refresh mode, use the testing time stamp.  And
+      // also we don't update mPreviousFrameTimeStamp since unlike normal
+      // refresh mode, on the testing mode animations on the compositor are
+      // synchronously composed, so we don't need to worry about the time gap
+      // between the main thread and compositor thread.
+      AnimationHelper::SampleAnimations(mAnimStorage, *testingTimeStamp);
+      return;
+    }
   }
 
-  TimeStamp animTime = testingTimeStamp.valueOr(
-    !mPreviousFrameTimeStamp.IsNull()
-    ? mPreviousFrameTimeStamp
-    : mCompositorScheduler->GetLastComposeTime());
-
-
-  AnimationHelper::SampleAnimations(mAnimStorage, animTime);
+  TimeStamp lastComposeTime = mCompositorScheduler->GetLastComposeTime();
+  // if we have already mPreviousTimeStamp, use it since on the compositor the
+  // time in the previous tick is more closer to the main-thread tick time.
+  AnimationHelper::SampleAnimations(mAnimStorage,
+      !mPreviousFrameTimeStamp.IsNull()
+      ? mPreviousFrameTimeStamp
+      : lastComposeTime);
 
   // Reset the previous time stamp if we don't already have any running
   // animations to avoid using the time which is far behind for newly
   // started animations.
   mPreviousFrameTimeStamp =
-    mAnimStorage->AnimatedValueCount() ? animTime : TimeStamp();
+    mAnimStorage->AnimatedValueCount() ? lastComposeTime : TimeStamp();
 }
 
 void
 WebRenderBridgeParent::SampleAnimations(nsTArray<wr::WrOpacityProperty>& aOpacityArray,
                                         nsTArray<wr::WrTransformProperty>& aTransformArray)
 {
   AdvanceAnimations();