Migrate test block 9 to Dart 2.0

tests/corelib_2/hashcode_test.dart

Index: tests/corelib_2/hashcode_test.dart
diff --git a/tests/corelib_strong/hashcode_test.dart b/tests/corelib_2/hashcode_test.dart
similarity index 93%
rename from tests/corelib_strong/hashcode_test.dart
rename to tests/corelib_2/hashcode_test.dart
index ba452759175452ce1e2f16024f82e17e97e0eea7..840df023113d5baf3227cb4822321a8b34bf488e 100644
--- a/tests/corelib_strong/hashcode_test.dart
+++ b/tests/corelib_2/hashcode_test.dart
@@ -11,8 +11,7 @@ class Override {
 
   int foo() => hash; //   Just some function that can be closurized.
 
-  bool operator ==(Object other) =>
-      other is Override && (other as Override).hash == hash;
+  bool operator ==(Object other) => other is Override && other.hash == hash;
 }
 
 int bar() => 42; // Some global function.