diff --git a/gfx/layers/apz/src/APZCTreeManager.cpp b/gfx/layers/apz/src/APZCTreeManager.cpp
index 786ec5ec494a..d193d851468b 100644
--- a/gfx/layers/apz/src/APZCTreeManager.cpp
+++ b/gfx/layers/apz/src/APZCTreeManager.cpp
@@ -453,9 +453,9 @@ APZCTreeManager::PrepareNodeForLayer(const LayerMetricsWrapper& aLayer,
     // we are logging about APZCs is the scroll id, and otherwise we could
     // confuse APZCs from different layer trees with the same scroll id.
     if (aLayersId == aState.mOriginatingLayersId) {
-      if (apzc->IsRootForLayersId()) {
+      if (apzc->HasNoParentWithSameLayersId()) {
         aState.mPaintLogger.LogTestData(aMetrics.GetScrollId(),
-            "isRootForLayersId", true);
+            "hasNoParentWithSameLayersId", true);
       } else {
         MOZ_ASSERT(apzc->GetParent());
         aState.mPaintLogger.LogTestData(aMetrics.GetScrollId(),
@@ -464,7 +464,7 @@ APZCTreeManager::PrepareNodeForLayer(const LayerMetricsWrapper& aLayer,
     }
 
     if (newApzc) {
-      if (apzc->IsRootForLayersId()) {
+      if (apzc->HasNoParentWithSameLayersId()) {
         // If we just created a new apzc that is the root for its layers ID, then
         // we need to update its zoom constraints which might have arrived before this
         // was created
@@ -1040,7 +1040,7 @@ APZCTreeManager::UpdateZoomConstraints(const ScrollableLayerGuid& aGuid,
 
   // For a given layers id, non-root APZCs inherit the zoom constraints
   // of their root.
-  if (node && node->GetApzc()->IsRootForLayersId()) {
+  if (node && node->GetApzc()->HasNoParentWithSameLayersId()) {
     UpdateZoomConstraintsRecursively(node.get(), aConstraints);
   }
 }
@@ -1057,7 +1057,7 @@ APZCTreeManager::UpdateZoomConstraintsRecursively(HitTestingTreeNode* aNode,
   }
   for (HitTestingTreeNode* child = aNode->GetLastChild(); child; child = child->GetPrevSibling()) {
     // We can have subtrees with their own layers id - leave those alone.
-    if (child->GetApzc() && child->GetApzc()->IsRootForLayersId()) {
+    if (child->GetApzc() && child->GetApzc()->HasNoParentWithSameLayersId()) {
       continue;
     }
     UpdateZoomConstraintsRecursively(child, aConstraints);
@@ -1344,7 +1344,7 @@ APZCTreeManager::BuildOverscrollHandoffChain(const nsRefPtr<AsyncPanZoomControll
     result->Add(apzc);
 
     if (apzc->GetScrollHandoffParentId() == FrameMetrics::NULL_SCROLL_ID) {
-      if (!apzc->IsRootForLayersId()) {
+      if (!apzc->HasNoParentWithSameLayersId()) {
         // This probably indicates a bug or missed case in layout code
         NS_WARNING("Found a non-root APZ with no handoff parent");
       }
@@ -1362,7 +1362,7 @@ APZCTreeManager::BuildOverscrollHandoffChain(const nsRefPtr<AsyncPanZoomControll
     // scroll id.
     AsyncPanZoomController* scrollParent = nullptr;
     AsyncPanZoomController* parent = apzc;
-    while (!parent->IsRootForLayersId()) {
+    while (!parent->HasNoParentWithSameLayersId()) {
       parent = parent->GetParent();
       // While walking up to find the root of the subtree, if we encounter the
       // handoff parent, we don't actually need to do the search so we can
@@ -1705,7 +1705,7 @@ APZCTreeManager::RootAPZCForLayersId(AsyncPanZoomController* aApzc) const
 {
   MonitorAutoLock lock(mTreeLock);
   nsRefPtr<AsyncPanZoomController> apzc = aApzc;
-  while (apzc && !apzc->IsRootForLayersId()) {
+  while (apzc && !apzc->HasNoParentWithSameLayersId()) {
     apzc = apzc->GetParent();
   }
   return apzc.forget();
diff --git a/gfx/layers/apz/src/AsyncPanZoomController.h b/gfx/layers/apz/src/AsyncPanZoomController.h
index 0f3f17c474e9..691f297cec46 100644
--- a/gfx/layers/apz/src/AsyncPanZoomController.h
+++ b/gfx/layers/apz/src/AsyncPanZoomController.h
@@ -899,9 +899,10 @@ public:
   }
 
   /* Returns true if there is no APZC higher in the tree with the same
-   * layers id.
+   * layers id. Deprecated. New code shouldn't use this. Old code should be
+   * updated to not use this.
    */
-  bool IsRootForLayersId() const {
+  bool HasNoParentWithSameLayersId() const {
     return !mParent || (mParent->mLayersId != mLayersId);
   }
 
diff --git a/gfx/layers/apz/test/apz_test_utils.js b/gfx/layers/apz/test/apz_test_utils.js
index a4ae85ce5a8e..834afd8970e5 100644
--- a/gfx/layers/apz/test/apz_test_utils.js
+++ b/gfx/layers/apz/test/apz_test_utils.js
@@ -91,7 +91,7 @@ function buildApzcTree(paint) {
   // This 'root' does not correspond to an APZC.
   var root = makeNode(-1);
   for (var scrollId in paint) {
-    if ("isRootForLayersId" in paint[scrollId]) {
+    if ("hasNoParentWithSameLayersId" in paint[scrollId]) {
       addRoot(root, scrollId);
     } else if ("parentScrollId" in paint[scrollId]) {
       addLink(root, scrollId, paint[scrollId]["parentScrollId"]);