Remove DartString from constants.

pkg/compiler/lib/src/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend.namer;
 
 import 'dart:collection' show HashMap;
 
 import 'package:js_runtime/shared/embedded_names.dart' show JsGetName;
 
@@ skipping 1792 matching lines @@
   }
 
   @override
   void visitBool(BoolConstantValue constant, [_]) {
     add(constant.isTrue ? 'true' : 'false');
   }
 
   @override
   void visitString(StringConstantValue constant, [_]) {
     // No `addRoot` since string constants are always inlined.
-    addIdentifier(constant.primitiveValue.slowToString());
+    addIdentifier(constant.primitiveValue);
   }
 
   @override
   void visitList(ListConstantValue constant, [_]) {
     // TODO(9476): Incorporate type parameters into name.
     addRoot('List');
     int length = constant.length;
     if (constant.length == 0) {
       add('empty');
     } else if (length >= MAX_FRAGMENTS) {
@@ skipping 149 matching lines @@
     return _hashInt(constant.primitiveValue);
   }
 
   @override
   int visitDouble(DoubleConstantValue constant, [_]) {
     return _hashDouble(constant.primitiveValue);
   }
 
   @override
   int visitString(StringConstantValue constant, [_]) {
-    return _hashString(2, constant.primitiveValue.slowToString());
+    return _hashString(2, constant.primitiveValue);
   }
 
   @override
   int visitList(ListConstantValue constant, [_]) {
     return _hashList(constant.length, constant.entries);
   }
 
   @override
   int visitMap(MapConstantValue constant, [_]) {
     int hash = _hashList(constant.length, constant.keys);
@@ skipping 192 matching lines @@
   void addSuggestion(String original, String suggestion) {
     assert(!_suggestedNames.containsKey(original));
     _suggestedNames[original] = suggestion;
   }
 
   bool hasSuggestion(String original) => _suggestedNames.containsKey(original);
   bool isSuggestion(String candidate) {
     return _suggestedNames.containsValue(candidate);
   }
 }