WIP: Compute constant expressions in resolution.

pkg/compiler/lib/src/constants/constant_system.dart

Index: pkg/compiler/lib/src/constants/constant_system.dart
diff --git a/pkg/compiler/lib/src/constants/constant_system.dart b/pkg/compiler/lib/src/constants/constant_system.dart
index d99d795946700c3b8580fba918d6880352f36823..10830db6347fb541c17a1934d1a87e1118093b43 100644
--- a/pkg/compiler/lib/src/constants/constant_system.dart
+++ b/pkg/compiler/lib/src/constants/constant_system.dart
@@ -49,6 +49,7 @@ abstract class ConstantSystem {
   BinaryOperation get multiply;
   UnaryOperation get negate;
   UnaryOperation get not;
+  BinaryOperation get notEqual;
   BinaryOperation get shiftLeft;
   BinaryOperation get shiftRight;
   BinaryOperation get subtract;
@@ -73,6 +74,7 @@ abstract class ConstantSystem {
   // TODO(johnniwinther): Remove the need for [compiler].
   ConstantValue createType(Compiler compiler,
                            DartType type);
+  ConstantValue createSymbol(Compiler compiler, String text);
 
   // We need to special case the subtype check for JavaScript constant
   // system because an int is a double at runtime.
@@ -118,6 +120,7 @@ abstract class ConstantSystem {
       case BinaryOperatorKind.GT:   return greater;
       case BinaryOperatorKind.GTEQ:  return greaterEqual;
       case BinaryOperatorKind.EQ:  return equal;
+      case BinaryOperatorKind.NOT_EQ:  return notEqual;
       default:    return null;
     }
   }