Add support to populate custom context menu items.

LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu-expected.txt

Index: LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu-expected.txt
diff --git a/LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu-expected.txt b/LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..9b8f6ed785f858cf26f2153ee1746ec649964667
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+++ b/LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu-expected.txt
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+Tests the custom context menu items.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS itemsWithCustomContextMenu.length - items.length is 21
+PASS itemsWithCustomContextMenu[0] is "Item1"
+PASS itemsWithCustomContextMenu[4] is "Submenu >"
+PASS itemsWithCustomContextMenu[5] is "_Item4"
+PASS itemsWithCustomContextMenu[6] is "_Deeper submenu >"
+PASS itemsWithCustomContextMenu[7] is "__Item5"
+PASS itemsWithCustomContextMenu[8] is "__---------"
+PASS itemsWithCustomContextMenu[10] is "Item7"
+PASS itemsWithCustomContextMenu[11] is "---------"
+PASS itemsWithCustomContextMenu[12] is "Item8"
+PASS itemsWithCustomContextMenu[13] is "---------"
+PASS itemsWithCustomContextMenu[14] is "Item9"
+PASS itemsWithCustomContextMenu[16] is "---------"
+PASS itemsWithCustomContextMenu[19] is "---------"
+PASS itemsWithCustomContextMenu[20] is "Item13"
+PASS items1.length - items.length is 0
+PASS items2.length - items.length is 0
+PASS items3.length - items.length is 0
+PASS items4.length - items.length is 0
+PASS successfullyParsed is true
+
+TEST COMPLETE
+   
+