Use DOMSettableTokenList for {HTMLAnchorElement, HTMLAreaElement}.ping.

third_party/WebKit/LayoutTests/fast/dom/ping-attribute-dom-binding.html

Index: third_party/WebKit/LayoutTests/fast/dom/ping-attribute-dom-binding.html
diff --git a/third_party/WebKit/LayoutTests/fast/dom/ping-attribute-dom-binding.html b/third_party/WebKit/LayoutTests/fast/dom/ping-attribute-dom-binding.html
index b49b846c52d3b7b3dfff7f5bf3b00e6f5cf1086f..34fb537fc2c956658c0dd80f7632fddeb16a6982 100644
--- a/third_party/WebKit/LayoutTests/fast/dom/ping-attribute-dom-binding.html
+++ b/third_party/WebKit/LayoutTests/fast/dom/ping-attribute-dom-binding.html
@@ -9,24 +9,34 @@
 description('Tests the DOM bindings for the ping attribute');
 
 var anchor = document.createElement('a');
-shouldBeEqualToString('anchor.ping', '');
+shouldBe('anchor.ping', '[]');
 anchor.setAttribute('ping', 'p1');
-shouldBeEqualToString('anchor.ping', 'p1');
+shouldBe('anchor.ping', '["p1"]');
 anchor.ping = 'p2';
 shouldBeEqualToString('anchor.getAttribute("ping")', 'p2');
+anchor.ping.add('p3');

[philipj_slow, 2015/10/01 12:54:10]

If there isn't already another test doing it, also try adding a token that is
already present and verify that it does nothing.

+shouldBe('anchor.ping', '["p2","p3"]');
+shouldBeTrue('anchor.ping.contains("p3")');
+anchor.ping.remove('p2');
+shouldBe('anchor.ping', '["p3"]');
 anchor.ping = null;
 shouldBeEqualToString('anchor.getAttribute("ping")', 'null');
-shouldBeEqualToString('anchor.ping', 'null');
+shouldBe('anchor.ping', '["null"]');
 
 var area = document.createElement('area');
-shouldBeEqualToString('area.ping', '');
+shouldBe('area.ping', '[]');
 area.setAttribute('ping', 'p1');
-shouldBeEqualToString('area.ping', 'p1');
+shouldBe('area.ping', '["p1"]');
 area.ping = 'p2';
 shouldBeEqualToString('area.getAttribute("ping")', 'p2');
+area.ping.add('p3');
+shouldBe('area.ping', '["p2","p3"]');
+shouldBeTrue('area.ping.contains("p3")');
+area.ping.remove('p2');
+shouldBe('area.ping', '["p3"]');
 area.ping = null;
 shouldBeEqualToString('area.getAttribute("ping")', 'null');
-shouldBeEqualToString('area.ping', 'null');
+shouldBe('area.ping', '["null"]');
 
 </script>
 </body>