[dart2js] Make Selector.operator == an identical check.

Change-Id: Icd0d172d9234f1873d65793600dab1698569faf2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401262
Commit-Queue: Nate Biggs <[email protected]>
Reviewed-by: Nate Biggs <[email protected]>
Auto-Submit: Mayank Patke <[email protected]>
Commit-Queue: Mayank Patke <[email protected]>

Author: fishythefish

pkg/compiler/lib/src/universe/selector.dart

@@ -43,8 +43,7 @@ class Selector {
   final int hashCode;
 
   @override
-  bool operator ==(other) =>
-      identical(this, other) || other is Selector && hashCode == other.hashCode;
+  bool operator ==(other) => identical(this, other);
 
   int get argumentCount => callStructure.argumentCount;
   int get namedArgumentCount => callStructure.namedArgumentCount;