address comments

Author: mmalerba

src/cdk-experimental/scrolling/virtual-for-of.ts

@@ -271,8 +271,8 @@ export class CdkVirtualForOf<T> implements CollectionViewer, DoCheck, OnDestroy
         });
 
     // Update $implicit for any items that had an identity change.
-    changes.forEachIdentityChange((record: any) => {
-      const view = this._viewContainerRef.get(record.currentIndex) as
+    changes.forEachIdentityChange((record: IterableChangeRecord<T>) => {
+      const view = this._viewContainerRef.get(record.currentIndex!) as
           EmbeddedViewRef<CdkVirtualForOfContext<T>>;
       view.context.$implicit = record.item;
     });