Compute frontend/backend specific constants.

tests/compiler/dart2js_extra/minus_zero_test.dart

Index: tests/compiler/dart2js_extra/minus_zero_test.dart
diff --git a/tests/compiler/dart2js_extra/minus_zero_test.dart b/tests/compiler/dart2js_extra/minus_zero_test.dart
index a9d4722fbeee32e7072140ef2d60f72ac0e81c8d..9ef74323a86d7aeb7207ff1f7097a59bbf359677 100644
--- a/tests/compiler/dart2js_extra/minus_zero_test.dart
+++ b/tests/compiler/dart2js_extra/minus_zero_test.dart
@@ -6,13 +6,13 @@
 
 import "package:expect/expect.dart";
 
-const double MINUS_ZERO = -0;
+const double MINUS_ZERO = -0; /// 01: static type warning, checked mode compile-time error
 
 void main() {
   // Dart2js must not infer that the type-intersection of int and -0.0 is empty.
   // It must get an interceptor for the addition (`i += 3`), or use the native
   // JS + operation.
-  int i = MINUS_ZERO;
-  i += 3;
-  Expect.equals(3, i);
+  int i = MINUS_ZERO;  /// 01: continued
+  i += 3;              /// 01: continued
+  Expect.equals(3, i); /// 01: continued
 }