Remove deprecated StringBuffer.add, addAll and addCharCode.

sdk/lib/_internal/compiler/implementation/js_backend/runtime_types.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.
 
 part of js_backend;
 
 /// For each class, stores the possible class subtype tests that could succeed.
 abstract class TypeChecks {
   /// Get the set of checks required for class [element].
   Iterable<ClassElement> operator[](ClassElement element);
@@ skipping 282 matching lines @@
     map.putIfAbsent(cls, () => new Set<ClassElement>());
     map[cls].add(check);
   }
 
   Iterator<ClassElement> get iterator => map.keys.iterator;
 
   String toString() {
     StringBuffer sb = new StringBuffer();
     for (ClassElement holder in this) {
       for (ClassElement check in [holder]) {
-        sb.add('${holder.name.slowToString()}.${check.name.slowToString()}, ');
+        sb.write(
+            '${holder.name.slowToString()}.${check.name.slowToString()}, ');
       }
     }
     return '[$sb]';
   }
 }