Bug 1593381 - Add some new test-only APIs to WebRender[Layer]ScrollData. r=hiro

Differential Revision: https://phabricator.services.mozilla.com/D124291

gfx/layers/wr/WebRenderScrollData.cpp

@@ -143,6 +143,12 @@ const ScrollMetadata& WebRenderLayerScrollData::GetScrollMetadata(
   return aOwner.GetScrollMetadata(mScrollIds[aIndex]);
 }
 
+ScrollMetadata& WebRenderLayerScrollData::GetScrollMetadataMut(
+    WebRenderScrollData& aOwner, size_t aIndex) {
+  MOZ_ASSERT(aIndex < mScrollIds.Length());
+  return aOwner.GetScrollMetadataMut(mScrollIds[aIndex]);
+}
+
 CSSTransformMatrix WebRenderLayerScrollData::GetTransformTyped() const {
   return ViewAs<CSSTransformMatrix>(GetTransform());
 }
@@ -254,6 +260,11 @@ const ScrollMetadata& WebRenderScrollData::GetScrollMetadata(
   return mScrollMetadatas[aIndex];
 }
 
+ScrollMetadata& WebRenderScrollData::GetScrollMetadataMut(size_t aIndex) {
+  MOZ_ASSERT(aIndex < mScrollMetadatas.Length());
+  return mScrollMetadatas[aIndex];
+}
+
 Maybe<size_t> WebRenderScrollData::HasMetadataFor(
     const ScrollableLayerGuid::ViewID& aScrollId) const {
   auto ptr = mScrollIdMap.lookup(aScrollId);

gfx/layers/wr/WebRenderScrollData.h

@@ -180,6 +180,9 @@ class WebRenderLayerScrollData final {
   // GTests don't have a display list so they can't use Initialize().
   void InitializeForTest(int32_t aDescendantCount);
 
+  ScrollMetadata& GetScrollMetadataMut(WebRenderScrollData& aOwner,
+                                       size_t aIndex);
+
  private:
   // The number of descendants this layer has (not including the layer itself).
   // This is needed to reconstruct the depth-first layer tree traversal
@@ -267,6 +270,11 @@ class WebRenderScrollData {
   friend std::ostream& operator<<(std::ostream& aOut,
                                   const WebRenderScrollData& aData);
 
+ private:
+  // For test use only.
+  friend class WebRenderLayerScrollData;
+  ScrollMetadata& GetScrollMetadataMut(size_t aIndex);
+
  private:
   // This is called by the ParamTraits implementation to rebuild mScrollIdMap
   // based on mScrollMetadatas