Implement select listbox using shadow DOM

LayoutTests/platform/mac/fast/forms/hidden-listbox-expected.txt

Index: LayoutTests/platform/mac/fast/forms/hidden-listbox-expected.txt
diff --git a/LayoutTests/platform/mac/fast/forms/hidden-listbox-expected.txt b/LayoutTests/platform/mac/fast/forms/hidden-listbox-expected.txt
index f9da3f482d46d2fe63506d2f23bcac30d975a41b..2f88a3838024a1acb373b8f714ee950d5d181872 100644
--- a/LayoutTests/platform/mac/fast/forms/hidden-listbox-expected.txt
+++ b/LayoutTests/platform/mac/fast/forms/hidden-listbox-expected.txt
@@ -6,5 +6,9 @@ layer at (0,0) size 800x600
       RenderText {#text} at (0,0) size 510x18
         text run at (0,0) width 510: "This tests that the whole listbox control is hidden when visibility is set to hidden. "
       RenderBR {BR} at (510,14) size 0x0
-      RenderListBox {SELECT} at (0,18) size 179x57 [bgcolor=#FFFFFF] [border: (1px inset #808080)]
       RenderText {#text} at (0,0) size 0x0
+hidden layer at (8,26) size 179x58 clip at (9,27) size 166x56
+  RenderListBox {SELECT} at (0,18) size 178.84x58 [bgcolor=#FFFFFF] [border: (1px solid #999999)]
+    RenderBlock {OPTION} at (1,1) size 165.84x14
+      RenderText {#text} at (2,0) size 162x13
+        text run at (2,0) width 162: "This text should not be visible"