Revert 13878

lib/coreimpl/string_buffer.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.
 
 /**
  * The StringBuffer class is useful for concatenating strings
  * efficiently. Only on a call to [toString] are the strings
  * concatenated to a single String.
  */
 class StringBufferImpl implements StringBuffer {
   /**
    * Creates the string buffer with an initial content.
    */
   StringBufferImpl(Object content) {
     clear();
     add(content);
   }
 
   /**
    * Returns the length of the buffer.
    */
   int get length {
     return _length;
   }
 
   bool isEmpty() {
-    return _length == 0;
+    return _length === 0;
   }
 
   /**
    * Adds [obj] to the buffer. Returns [this].
    */
   StringBuffer add(Object obj) {
     String str = obj.toString();
-    if (str == null || str.isEmpty()) {
+    if (str === null || str.isEmpty()) {
       return this;
     }
     _buffer.add(str);
     _length += str.length;
     return this;
   }
 
   /**
    * Adds all items in [objects] to the buffer. Returns [this].
    */
@@ skipping 18 matching lines @@
   StringBuffer clear() {
     _buffer = new List<String>();
     _length = 0;
     return this;
   }
 
   /**
    * Returns the contents of buffer as a concatenated string.
    */
   String toString() {
-    if (_buffer.length == 0) return "";
-    if (_buffer.length == 1) return _buffer[0];
+    if (_buffer.length === 0) return "";
+    if (_buffer.length === 1) return _buffer[0];
     String result = StringImplementation.concatAll(_buffer);
     _buffer.clear();
     _buffer.add(result);
     // Since we track the length at each add operation, there is no
     // need to update it in this function.
     return result;
   }
 
   List<String> _buffer;
   int _length;
 }