[List] Use isKindOfClass to ensure there is support for all MDCShadowLayer's subclasses.

PiperOrigin-RevId: 353292179

Author: yarneo

components/List/src/MDCBaseCell.m

@@ -15,8 +15,10 @@
 #import "MDCBaseCell.h"
 #import "MDCSelfSizingLayoutAttributes.h"
 
+#import "MaterialElevation.h"
 #import "MaterialInk.h"
 #import "MaterialRipple.h"
+#import "MaterialShadowElevations.h"
 #import "MaterialShadowLayer.h"
 
 @interface MDCBaseCell ()
@@ -208,7 +210,7 @@ - (UIColor *)rippleColor {
 }
 
 - (MDCShadowLayer *)shadowLayer {
-  if ([self.layer isMemberOfClass:[MDCShadowLayer class]]) {
+  if ([self.layer isKindOfClass:[MDCShadowLayer class]]) {
     return (MDCShadowLayer *)self.layer;
   }
   return nil;