Implement select listbox using shadow DOM

Source/core/css/resolver/SharedStyleFinder.cpp

Index: Source/core/css/resolver/SharedStyleFinder.cpp
diff --git a/Source/core/css/resolver/SharedStyleFinder.cpp b/Source/core/css/resolver/SharedStyleFinder.cpp
index 4589e71bf6fdefbf4994106432cec0dcfe0eb9b5..ad6c69a457f041325f5b27e1ee975c9bfa69cf35 100644
--- a/Source/core/css/resolver/SharedStyleFinder.cpp
+++ b/Source/core/css/resolver/SharedStyleFinder.cpp
@@ -241,6 +241,10 @@ bool SharedStyleFinder::canShareStyleWithElement(Element& candidate) const
     if (isControl && !canShareStyleWithControl(candidate))
         return false;
 
+    if (isHTMLOptionElement(candidate) && isHTMLOptionElement(element())

[keishi, 2014/07/01 05:06:35]

This makes fast/forms/select-initial-position.html pass.
If we don't have this the style for the selected option can be shared with the
previous sibling not selected option.

+        && toHTMLOptionElement(candidate).selected() != toHTMLOptionElement(element()).selected())
+        return false;
+
     // FIXME: This line is surprisingly hot, we may wish to inline hasDirectionAuto into StyleResolver.
     if (candidate.isHTMLElement() && toHTMLElement(candidate).hasDirectionAuto())
         return false;