Context menu should skip any menu construct whose submenu label is the empty string.

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
index 9b8f6ed785f858cf26f2153ee1746ec649964667..38dc9852ea5e07f6681119a6e66de1dc2c1ca0a5 100644
--- a/LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu-expected.txt
+++ b/LayoutTests/fast/dom/HTMLMenuElement/custom-context-menu-expected.txt
@@ -3,21 +3,24 @@ 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.length - items.length is 17
 PASS itemsWithCustomContextMenu[0] is "Item1"
+PASS itemsWithCustomContextMenu[1] is "Item2"
+PASS itemsWithCustomContextMenu[2] is "---------"
+PASS itemsWithCustomContextMenu[3] is "Item3"
 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[9] is "__Item6"
 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 itemsWithCustomContextMenu[13] is "Item11"
+PASS itemsWithCustomContextMenu[14] is "Item12"
+PASS itemsWithCustomContextMenu[15] is "---------"
+PASS itemsWithCustomContextMenu[16] is "Item13"
 PASS items1.length - items.length is 0
 PASS items2.length - items.length is 0
 PASS items3.length - items.length is 0