Bug 1552608 - Make APZCTreeManager::GetTargetAPZC(layersId, scrollId) const. r=tnikkel

Differential Revision: https://phabricator.services.mozilla.com/D48377

--HG--
extra : moz-landing-system : lando

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -2548,7 +2548,8 @@ static bool GuidComparatorIgnoringPresShell(const ScrollableLayerGuid& aOne,
 }
 
 already_AddRefed<AsyncPanZoomController> APZCTreeManager::GetTargetAPZC(
-    const LayersId& aLayersId, const ScrollableLayerGuid::ViewID& aScrollId) {
+    const LayersId& aLayersId,
+    const ScrollableLayerGuid::ViewID& aScrollId) const {
   MutexAutoLock lock(mMapLock);
   ScrollableLayerGuid guid(aLayersId, 0, aScrollId);
   auto it = mApzcMap.find(guid);

gfx/layers/apz/src/APZCTreeManager.h

@@ -566,7 +566,8 @@ class APZCTreeManager : public IAPZCTreeManager, public APZInputBridge {
       LayersId* aOutLayersId,
       HitTestingTreeNodeAutoLock* aOutScrollbarNode = nullptr);
   already_AddRefed<AsyncPanZoomController> GetTargetAPZC(
-      const LayersId& aLayersId, const ScrollableLayerGuid::ViewID& aScrollId);
+      const LayersId& aLayersId,
+      const ScrollableLayerGuid::ViewID& aScrollId) const;
   ScreenToParentLayerMatrix4x4 GetScreenToApzcTransform(
       const AsyncPanZoomController* aApzc) const;
   ParentLayerToScreenMatrix4x4 GetApzcToGeckoTransform(