[dart2js] Remove _CanonicalizedTypeMaskKey and use record

Since #60419 is fixed by https://github.com/dart-lang/sdk/issues/60419,
we should be able to use record keys again.

Change-Id: I1256d74e80e135b0ba2a38c64c42e0463964baaf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/419986
Reviewed-by: Stephen Adams <sra@google.com>
Commit-Queue: Mayank Patke <fishythefish@google.com>

pkg/compiler/lib/src/inferrer/typemasks/masks.dart

@@ -43,25 +43,6 @@ part 'type_mask.dart';
 part 'union_type_mask.dart';
 part 'value_type_mask.dart';
 
-// TODO(60419): Go back to using a record as the key when it is no longer slower
-// than using a data class.
-final class _CanonicalizedTypeMaskKey {
-  final ClassEntity? _base;
-  final _Flags _flags;
-
-  const _CanonicalizedTypeMaskKey(this._base, this._flags);
-
-  @override
-  int get hashCode => Object.hash(_base, _flags);
-
-  @override
-  bool operator ==(Object other) =>
-      identical(this, other) ||
-      other is _CanonicalizedTypeMaskKey &&
-          _base == other._base &&
-          _flags == other._flags;
-}
-
 class CommonMasks with AbstractValueDomain {
   // TODO(sigmund): once we split out the backend common elements, depend
   // directly on those instead.
@@ -75,8 +56,7 @@ class CommonMasks with AbstractValueDomain {
 
   final Map<TypeMask, Map<TypeMask, TypeMask>> _intersectionCache = {};
 
-  final Map<_CanonicalizedTypeMaskKey, FlatTypeMask> _canonicalizedTypeMasks =
-      {};
+  final Map<(ClassEntity?, _Flags), FlatTypeMask> _canonicalizedTypeMasks = {};
 
   /// Return the cached mask for [base] with the given flags, or calls
   /// [createMask] to create the mask and cache it.
@@ -84,10 +64,7 @@ class CommonMasks with AbstractValueDomain {
     ClassEntity? base,
     _Flags flags,
     FlatTypeMask Function() createMask,
-  ) => _canonicalizedTypeMasks.putIfAbsent(
-    _CanonicalizedTypeMaskKey(base, flags),
-    createMask,
-  );
+  ) => _canonicalizedTypeMasks.putIfAbsent((base, flags), createMask);
 
   @override
   late final TypeMask internalTopType = TypeMask.subclass(