Implement icon attribute for menuitem

LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu.html

Index: LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu.html
diff --git a/LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu.html b/LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu.html
index 3d9944799319c4a23481d25eb7d44776f3d98eb4..17f54706bcd95fee8f14ce8e0c25ac3addc918f5 100644
--- a/LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu.html
+++ b/LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu.html
@@ -55,6 +55,7 @@
         <menuitem type="checkbox" label="Item15" checked></menuitem>
         <!-- Test default menuitem with "checked" attribute. -->
         <menuitem label="Item16" checked></menuitem>
+        <menuitem label="Item17" icon="abc.png" checked></menuitem>
         <!-- Test removal of separator at the end. -->
         <hr>
     </menu>
@@ -160,7 +161,7 @@ eventSender.keyDown("escape");
 var button5 = document.getElementById("button_5");
 var items5 = contextClickAndGetMenuItems(button5);
 
-shouldBeEqualToNumber("itemsWithCustomContextMenu.length - items.length", 20);
+shouldBeEqualToNumber("itemsWithCustomContextMenu.length - items.length", 21);
 shouldBeEqualToString("itemsWithCustomContextMenu[0]", "Item1");
 shouldBeEqualToString("itemsWithCustomContextMenu[1]", "#Item2");
 shouldBeEqualToString("itemsWithCustomContextMenu[2]", "---------");
@@ -181,6 +182,7 @@ shouldBeEqualToString("itemsWithCustomContextMenu[16]", "Item13");
 shouldBeEqualToString("itemsWithCustomContextMenu[17]", "Item14");
 shouldBeEqualToString("itemsWithCustomContextMenu[18]", "*Item15");
 shouldBeEqualToString("itemsWithCustomContextMenu[19]", "Item16");
+shouldBeEqualToString("itemsWithCustomContextMenu[20]", "Item17abc.png");
 shouldBeEqualToNumber("items1.length - items.length", 0);
 shouldBeEqualToNumber("items2.length - items.length", 0);
 shouldBeEqualToNumber("items3.length - items.length", 0);