a === b -> identical(a, b)

utils/css/tokenizer_base.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.
 // Generated by scripts/tokenizer_gen.py.
 
 
 abstract class TokenSource {
   Token next();
 }
 
@@ skipping 162 matching lines @@
       return c - 87;
     } else if (c >= 65/*A*/ && c <= 70/*F*/) {
       return c - 55;
     } else {
       return -1;
     }
   }
 
   int readHex([int hexLength]) {
     int maxIndex;
-    if (hexLength === null) {
+    if (hexLength == null) {
       maxIndex = _text.length - 1;
     } else {
       // TODO(jimhug): What if this is too long?
       maxIndex = _index + hexLength;
       if (maxIndex >= _text.length) return -1;
     }
     var result = 0;
     while (_index < maxIndex) {
       final digit = _hexDigit(_text.charCodeAt(_index));
       if (digit == -1) {
-        if (hexLength === null) {
+        if (hexLength == null) {
           return result;
         } else {
           return -1;
         }
       }
       _hexDigit(_text.charCodeAt(_index));
       // Multiply by 16 rather than shift by 4 since that will result in a
       // correct value for numbers that exceed the 32 bit precision of JS
       // 'integers'.
       // TODO: Figure out a better solution to integer truncation. Issue 638.
@@ skipping 240 matching lines @@
     }
     int kind = getIdentifierKind();
     if (kind == TokenKind.IDENTIFIER) {
       return _finishToken(TokenKind.IDENTIFIER);
     } else {
       return _finishToken(kind);
     }
   }
 }