Remove deprecated Strings class.

sdk/lib/_internal/dartdoc/lib/dartdoc.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.
 
 /**
  * To generate docs for a library, run this script with the path to an
  * entrypoint .dart file, like:
  *
  *     $ dart dartdoc.dart foo.dart
  *
@@ skipping 673 matching lines @@
       final List typeMembers = docMembersJson(type.members);
       if (!typeMembers.isEmpty) {
         typeInfo[MEMBERS] = typeMembers;
       }
 
       if (!type.originalDeclaration.typeVariables.isEmpty) {
         final typeVariables = [];
         for (final typeVariable in type.originalDeclaration.typeVariables) {
           typeVariables.add(typeVariable.displayName);
         }
-        typeInfo[ARGS] = Strings.join(typeVariables, ', ');
+        typeInfo[ARGS] = typeVariables.join(', ');
       }
       types.add(typeInfo);
     }
     if (!types.isEmpty) {
       libraryInfo[TYPES] = types;
     }
 
     libraryList.add(libraryInfo);
   }
 
@@ skipping 1054 matching lines @@
             !typeParam.upperBound.isObject) {
           final bound = typeName(typeParam.upperBound, showBounds: true);
           typeParams.add('${typeParam.simpleName} extends $bound');
         } else {
           typeParams.add(typeParam.simpleName);
         }
       }
       if (typeParams.isEmpty) {
         return type.simpleName;
       }
-      final params = Strings.join(typeParams, ', ');
+      final params = typeParams.join(', ');
       return '${type.simpleName}<$params>';
     }
 
     // See if it's an instantiation of a generic type.
     final typeArgs = type.typeArguments;
     if (typeArgs.length > 0) {
-      final args =
-          Strings.join(typeArgs.map((arg) => typeName(arg)), ', ');
+      final args = typeArgs.map((arg) => typeName(arg)).join(', ');
       return '${type.originalDeclaration.simpleName}<$args>';
     }
 
     // Regular type.
     return type.simpleName;
   }
 
   /**
    * Remove leading indentation to line up with first line.
    */
   unindentCode(SourceLocation span) {
     final column = span.column;
     final lines = span.text.split('\n');
     // TODO(rnystrom): Dirty hack.
     for (var i = 1; i < lines.length; i++) {
       lines[i] = unindent(lines[i], column);
     }
 
-    final code = Strings.join(lines, '\n');
+    final code = lines.join('\n');
     return code;
   }
 
   /**
    * Takes a string of Dart code and turns it into sanitized HTML.
    */
   formatCode(SourceLocation span) {
     final code = unindentCode(span);
 
     // Syntax highlight.
@@ skipping 197 matching lines @@
    return '''
         <div class="mdn">
         $mdnComment
         <div class="mdn-note"><a href="$mdnUrl">from MDN</a></div>
         </div>
         ''';
   }
 
   String toString() => mdnComment;
 }