--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -3635,37 +3635,49 @@ nsDOMWindowUtils::DispatchEventToChromeO
   *aRetVal = false;
   NS_ENSURE_STATE(aTarget && aEvent);
   aEvent->WidgetEventPtr()->mFlags.mOnlyChromeDispatch = true;
   *aRetVal = aTarget->
     DispatchEvent(*aEvent, CallerType::System, IgnoreErrors());
   return NS_OK;
 }
 
+static Result<nsIFrame*, nsresult>
+GetTargetFrame(const Element* aElement, const nsAString& aPseudoElement)
+{
+  nsIFrame* frame = aElement->GetPrimaryFrame();
+  if (!aPseudoElement.IsEmpty()) {
+    if (aPseudoElement.EqualsLiteral("::before")) {
+      frame = nsLayoutUtils::GetBeforeFrame(aElement);
+    } else if (aPseudoElement.EqualsLiteral("::after")) {
+      frame = nsLayoutUtils::GetAfterFrame(aElement);
+    } else {
+      return Err(NS_ERROR_INVALID_ARG);
+    }
+  }
+  return frame;
+}
+
 NS_IMETHODIMP
 nsDOMWindowUtils::GetOMTAStyle(Element* aElement,
                                const nsAString& aProperty,
                                const nsAString& aPseudoElement,
                                nsAString& aResult)
 {
   if (!aElement) {
     return NS_ERROR_INVALID_ARG;
   }
 
+  auto frameOrError = GetTargetFrame(aElement, aPseudoElement);
+  if (frameOrError.isErr()) {
+    return frameOrError.unwrapErr();
+  }
+  nsIFrame* frame = frameOrError.unwrap();
+
   RefPtr<nsROCSSPrimitiveValue> cssValue = nullptr;
-  nsIFrame* frame = aElement->GetPrimaryFrame();
-  if (!aPseudoElement.IsEmpty()) {
-    if (aPseudoElement.EqualsLiteral("::before")) {
-      frame = nsLayoutUtils::GetBeforeFrame(aElement);
-    } else if (aPseudoElement.EqualsLiteral("::after")) {
-      frame = nsLayoutUtils::GetAfterFrame(aElement);
-    } else {
-      return NS_ERROR_INVALID_ARG;
-    }
-  }
   if (frame && nsLayoutUtils::AreAsyncAnimationsEnabled()) {
     RefPtr<LayerManager> widgetLayerManager;
     if (nsIWidget* widget = GetWidget()) {
       widgetLayerManager = widget->GetLayerManager();
     }
 
     if (aProperty.EqualsLiteral("opacity")) {
       float value = 0;
@@ -3728,16 +3740,73 @@ nsDOMWindowUtils::GetOMTAStyle(Element* 
     cssValue->GetCssText(text, rv);
     aResult.Assign(text);
     return rv.StealNSResult();
   }
   aResult.Truncate();
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDOMWindowUtils::GetOMTCTransform(Element* aElement,
+                                   const nsAString& aPseudoElement,
+                                   nsAString& aResult)
+{
+  if (!aElement) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (GetWebRenderBridge()) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+
+  auto frameOrError = GetTargetFrame(aElement, aPseudoElement);
+  if (frameOrError.isErr()) {
+    return frameOrError.unwrapErr();
+  }
+
+  nsIFrame* frame = frameOrError.unwrap();
+  aResult.Truncate();
+  if (!frame) {
+    return NS_OK;
+  }
+
+  Layer* layer =
+    FrameLayerBuilder::GetDedicatedLayer(frame,
+                                         DisplayItemType::TYPE_TRANSFORM);
+  if (!layer) {
+    return NS_OK;
+  }
+
+  ShadowLayerForwarder* forwarder = layer->Manager()->AsShadowForwarder();
+  if (!forwarder || !forwarder->HasShadowManager()) {
+    return NS_OK;
+  }
+
+  MaybeTransform transform;
+  forwarder->GetShadowManager()->
+    SendGetTransform(layer->AsShadowableLayer()->GetShadow(), &transform);
+  if (transform.type() != MaybeTransform::TMatrix4x4) {
+    return NS_OK;
+  }
+
+  Matrix4x4 matrix = transform.get_Matrix4x4();
+  RefPtr<nsROCSSPrimitiveValue> cssValue =
+    nsComputedDOMStyle::MatrixToCSSValue(matrix);
+  if (!cssValue) {
+    return NS_OK;
+  }
+
+  nsAutoString text;
+  ErrorResult rv;
+  cssValue->GetCssText(text, rv);
+  aResult.Assign(text);
+  return rv.StealNSResult();
+}
+
 namespace {
 
 class HandlingUserInputHelper final : public nsIJSRAIIHelper
 {
 public:
   explicit HandlingUserInputHelper(bool aHandlingUserInput);
 
   NS_DECL_ISUPPORTS

--- a/dom/interfaces/base/nsIDOMWindowUtils.idl
+++ b/dom/interfaces/base/nsIDOMWindowUtils.idl
@@ -1692,16 +1692,25 @@ interface nsIDOMWindowUtils : nsISupport
   /*
    * Returns the value of a given property animated on the compositor thread.
    * If the property is NOT currently being animated on the compositor thread,
    * returns an empty string.
    */
   AString getOMTAStyle(in Element aElement, in AString aProperty,
                        [optional] in AString aPseudoElement);
 
+  /*
+   * Returns the value of the transform value on the compositor thread.
+   * Unlike the above getOMTAStyle, the transform value returned by this
+   * includes both of animating and APZ values.
+   * Note: This function doesn't work on WebRender at all.
+   */
+  AString getOMTCTransform(in Element aElement,
+                           [optional] in AString aPseudoElement);
+
   /**
    * If aHandlingInput is true, this informs the event state manager that
    * we're handling user input. Otherwise, this is a no-op (as by default
    * we're not handling user input).
    * Remember to call destruct() on the return value!
    * See also nsIDOMWindowUtils::isHandlingUserInput.
    */
   nsIJSRAIIHelper setHandlingUserInput(in boolean aHandlingInput);