Implement select element list box with shadow DOM.

LayoutTests/platform/chromium-linux/fast/forms/option-strip-whitespace-expected.txt

Index: LayoutTests/platform/chromium-linux/fast/forms/option-strip-whitespace-expected.txt
diff --git a/LayoutTests/platform/chromium-linux/fast/forms/option-strip-whitespace-expected.txt b/LayoutTests/platform/chromium-linux/fast/forms/option-strip-whitespace-expected.txt
index eecba77d91a786b7baf0fa62e33be54856b81bf5..c597015d40661ed4907c5a49d972e3e3ac76c0ce 100644
--- a/LayoutTests/platform/chromium-linux/fast/forms/option-strip-whitespace-expected.txt
+++ b/LayoutTests/platform/chromium-linux/fast/forms/option-strip-whitespace-expected.txt
@@ -6,37 +6,45 @@ layer at (0,0) size 800x600
       RenderBlock {P} at (0,0) size 784x20
         RenderText {#text} at (0,0) size 383x19
           text run at (0,0) width 383: "All of these selects should have the same amount of whitespace."
-      RenderBlock (anonymous) at (0,36) size 784x298
-        RenderText {#text} at (0,51) size 67x19
-          text run at (0,51) width 67: "Five Tabs: "
-        RenderListBox {SELECT} at (69,2) size 76x69 [bgcolor=#FFFFFF] [border: (1px inset #808080)]
-        RenderBR {BR} at (147,66) size 0x0
-        RenderBR {BR} at (0,73) size 0x19
-        RenderText {#text} at (0,144) size 81x19
-          text run at (0,144) width 81: "Five Spaces: "
-        RenderListBox {SELECT} at (83,95) size 76x69 [bgcolor=#FFFFFF] [border: (1px inset #808080)]
-        RenderBR {BR} at (161,159) size 0x0
-        RenderBR {BR} at (0,166) size 0x19
-        RenderText {#text} at (0,188) size 280x19
-          text run at (0,188) width 280: "Five Spaces (with leading/trailing whitespace): "
-        RenderMenuList {SELECT} at (282,188) size 96x20 [bgcolor=#DDDDDD] [border: (1px solid #000000)]
+      RenderBlock (anonymous) at (0,36) size 784x300
+        RenderText {#text} at (0,54) size 67x19
+          text run at (0,54) width 67: "Five Tabs: "
+        RenderBR {BR} at (147,69) size 0x0
+        RenderBR {BR} at (0,74) size 0x19
+        RenderText {#text} at (0,148) size 81x19
+          text run at (0,148) width 81: "Five Spaces: "
+        RenderBR {BR} at (161,163) size 0x0
+        RenderBR {BR} at (0,168) size 0x19
+        RenderText {#text} at (0,190) size 280x19
+          text run at (0,190) width 280: "Five Spaces (with leading/trailing whitespace): "
+        RenderMenuList {SELECT} at (282,190) size 96x20 [bgcolor=#DDDDDD] [border: (1px solid #000000)]
           RenderBlock (anonymous) at (1,1) size 94x18
             RenderText at (4,1) size 71x16
               text run at (4,1) width 71: "Five Spaces"
-        RenderBR {BR} at (380,203) size 0x0
-        RenderBR {BR} at (0,210) size 0x19
-        RenderText {#text} at (0,232) size 266x19
-          text run at (0,232) width 266: "Five Tabs (with leading/trailing whitespace): "
-        RenderMenuList {SELECT} at (268,232) size 80x20 [bgcolor=#DDDDDD] [border: (1px solid #000000)]
+        RenderBR {BR} at (380,205) size 0x0
+        RenderBR {BR} at (0,212) size 0x19
+        RenderText {#text} at (0,234) size 266x19
+          text run at (0,234) width 266: "Five Tabs (with leading/trailing whitespace): "
+        RenderMenuList {SELECT} at (268,234) size 80x20 [bgcolor=#DDDDDD] [border: (1px solid #000000)]
           RenderBlock (anonymous) at (1,1) size 78x18
             RenderText at (4,1) size 55x16
               text run at (4,1) width 55: "Five Tabs"
-        RenderBR {BR} at (350,247) size 0x0
-        RenderBR {BR} at (0,254) size 0x19
-        RenderText {#text} at (0,276) size 121x19
-          text run at (0,276) width 121: "Mixed Whitespace: "
-        RenderMenuList {SELECT} at (123,276) size 80x20 [bgcolor=#DDDDDD] [border: (1px solid #000000)]
+        RenderBR {BR} at (350,249) size 0x0
+        RenderBR {BR} at (0,256) size 0x19
+        RenderText {#text} at (0,278) size 121x19
+          text run at (0,278) width 121: "Mixed Whitespace: "
+        RenderMenuList {SELECT} at (123,278) size 80x20 [bgcolor=#DDDDDD] [border: (1px solid #000000)]
           RenderBlock (anonymous) at (1,1) size 78x18
             RenderText at (4,1) size 55x16
               text run at (4,1) width 55: "Five Tabs"
         RenderText {#text} at (0,0) size 0x0
+layer at (77,46) size 76x69 clip at (78,47) size 59x67
+  RenderListBox {SELECT} at (69,2) size 76x69 [bgcolor=#FFFFFF] [border: (1px inset #808080)]
+    RenderBlock {OPTION} at (1,1) size 59x16
+      RenderText {#text} at (2,0) size 55x16
+        text run at (2,0) width 55: "Five Tabs"
+layer at (91,140) size 76x69 clip at (92,141) size 59x67
+  RenderListBox {SELECT} at (83,96) size 76x69 [bgcolor=#FFFFFF] [border: (1px inset #808080)]
+    RenderBlock {OPTION} at (1,1) size 59x16
+      RenderText {#text} at (2,0) size 55x16
+        text run at (2,0) width 55: "Five Tabs"