use proper notation for true, false, and null in doc comments

sdk/lib/_internal/compiler/implementation/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.
 
 part of js_backend;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class Namer implements ClosureNamer {
@@ skipping 706 matching lines @@
     element = backend.getImplementationClass(element);
     String name = getPrimitiveInterceptorRuntimeName(element);
     // TODO(ahe): Creating a string here is unfortunate. It is slow (due to
     // string concatenation in the implementation), and may prevent
     // segmentation of '$'.
     return name != null ? name : getNameForRti(element);
   }
 
   /**
    * Return a string to be used as the runtime name of this class (instead of
-   * the class name) or [null] if the class name should be used.
+   * the class name) or [:null:] if the class name should be used.
    */
   String getPrimitiveInterceptorRuntimeName(Element cls) {
     JavaScriptBackend backend = compiler.backend;
     if (cls == backend.jsIntClass) {
       return 'int';
     } else if (cls == backend.jsNumberClass) {
       return 'num';
     } else if (cls == backend.jsBoolClass) {
       return 'bool';
     } else if (cls == backend.jsDoubleClass) {
@@ skipping 653 matching lines @@
         if (!first) {
           sb.write('_');
         }
         sb.write('_');
         visit(link.head);
         first = true;
       }
     }
   }
 }