DOMTokenList should unify duplicated tokens.

third_party/WebKit/LayoutTests/fast/dom/HTMLElement/resources/class-list.js

 description('Tests the classList attribute and its properties.');
 
 var element;
 
 function createElement(className)
 {
     element = document.createElement('p');
     element.className = className;
 }
 
@@ skipping 12 matching lines @@
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/001.htm
 createElement('');
 shouldEvaluateTo('element.classList.length', 0);
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/002.htm
 createElement('x');
 shouldEvaluateTo('element.classList.length', 1);
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/003.htm
 createElement('x x');
-shouldEvaluateTo('element.classList.length', 2);
+shouldEvaluateTo('element.classList.length', 1);
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/004.htm
 createElement('x y');
 shouldEvaluateTo('element.classList.length', 2);
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/005.htm
 createElement('');
 element.classList.add('x');
 shouldBeEqualToString('element.className', 'x');
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/006.htm
 createElement('x');
 element.classList.add('x');
 shouldBeEqualToString('element.className', 'x');
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/007.htm
 createElement('x  x');
 element.classList.add('x');
-shouldBeEqualToString('element.className', 'x x');
+shouldBeEqualToString('element.className', 'x');
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/008.htm
 createElement('y');
 element.classList.add('x');
 shouldBeEqualToString('element.className', 'y x');
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/009.htm
 createElement('');
 element.classList.remove('x');
 shouldBeEqualToString('element.className', '');
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/010.htm
 createElement('x');
 element.classList.remove('x');
 shouldBeEqualToString('element.className', '');
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/011.htm
 createElement(' y x  y ');
 element.classList.remove('x');
-shouldBeEqualToString('element.className', 'y y');
+shouldBeEqualToString('element.className', 'y');
 
 // http://simon.html5.org/test/html/dom/reflecting/DOMTokenList/getting/012.htm
 createElement(' x y  x ');
 element.classList.remove('x');
 shouldBeEqualToString('element.className', 'y');
 
 
 debug('Ensure that we can handle empty class name correctly');
 element = document.createElement('span');
 shouldBeTrue("element.classList.toggle('x')");
@@ skipping 111 matching lines @@
 createElement('');
 shouldThrow("element.classList.toggle()");
 
 debug('Indexing');
 
 createElement('x');
 shouldBeEqualToString('element.classList[0]', 'x');
 shouldBeEqualToString('element.classList.item(0)', 'x');
 
 createElement('x x');
-shouldBeEqualToString('element.classList[1]', 'x');
-shouldBeEqualToString('element.classList.item(1)', 'x');
+shouldBeUndefined('element.classList[1]');
+shouldBeNull('element.classList.item(1)');
 
 createElement('x y');
 shouldBeEqualToString('element.classList[1]', 'y');
 shouldBeEqualToString('element.classList.item(1)', 'y');
 
 createElement('');
 shouldBeUndefined('element.classList[0]');
 shouldBeNull('element.classList.item(0)');
 
 createElement('x y z');
@@ skipping 148 matching lines @@
 element.classList.remove('a', 'c');
 shouldBe('observer.takeRecords().length', '1');
 
 // iterable<DOMString>;
 createElement('a b c');
 var seen = [];
 for (var t of element.classList) {
     seen.push(t);
 }
 shouldBeTrue("areArraysEqual(seen, ['a', 'b', 'c'])");