Remove DartString from constants.

pkg/compiler/lib/src/js_emitter/constant_ordering.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.js_emitter.constant_ordering;
 
 import '../constants/values.dart';
 import '../elements/elements.dart' show Elements;
 import '../elements/entities.dart' show Entity, FieldEntity;
 import '../elements/resolution_types.dart';
 import '../js_backend/js_backend.dart' show SyntheticConstantKind;
-import '../tree/dartstring.dart' show DartString;
 
 /// A canonical but arbitrary ordering of constants. The ordering is 'stable'
 /// under perturbation of the source.
 int deepCompareConstants(ConstantValue a, ConstantValue b) {
   return _CompareVisitor.compareValues(a, b);
 }
 
 class _CompareVisitor implements ConstantValueVisitor<int, ConstantValue> {
   const _CompareVisitor();
 
@@ skipping 65 matching lines @@
     return a.primitiveValue.compareTo(b.primitiveValue);
   }
 
   int visitBool(BoolConstantValue a, BoolConstantValue b) {
     int aInt = a.primitiveValue ? 1 : 0;
     int bInt = b.primitiveValue ? 1 : 0;
     return aInt.compareTo(bInt);
   }
 
   int visitString(StringConstantValue a, StringConstantValue b) {
-    DartString aString = a.primitiveValue;
-    DartString bString = b.primitiveValue;
-    int r = aString.length.compareTo(bString.length);
-    if (r != 0) return r;
-    return aString.slowToString().compareTo(bString.slowToString());
+    String aString = a.primitiveValue;
+    String bString = b.primitiveValue;
+    return aString.compareTo(bString);
   }
 
   int visitList(ListConstantValue a, ListConstantValue b) {
     int r = compareLists(compareValues, a.entries, b.entries);
     if (r != 0) return r;
     ResolutionInterfaceType type1 = a.type;
     ResolutionInterfaceType type2 = b.type;
     return compareDartTypes(type1, type2);
   }
 
@@ skipping 101 matching lines @@
   int visitBool(BoolConstantValue a, _) => BOOL;
   int visitString(StringConstantValue a, _) => STRING;
   int visitList(ListConstantValue a, _) => LIST;
   int visitMap(MapConstantValue a, _) => MAP;
   int visitConstructed(ConstructedConstantValue a, _) => CONSTRUCTED;
   int visitType(TypeConstantValue a, _) => TYPE;
   int visitInterceptor(InterceptorConstantValue a, _) => INTERCEPTOR;
   int visitSynthetic(SyntheticConstantValue a, _) => SYNTHETIC;
   int visitDeferred(DeferredConstantValue a, _) => DEFERRED;
 }