Don't render border images when border-style is none

third_party/WebKit/LayoutTests/scrollbars/listbox-scrollbar-combinations.html

Index: third_party/WebKit/LayoutTests/scrollbars/listbox-scrollbar-combinations.html
diff --git a/third_party/WebKit/LayoutTests/scrollbars/listbox-scrollbar-combinations.html b/third_party/WebKit/LayoutTests/scrollbars/listbox-scrollbar-combinations.html
index f451a579901d6bea7c85974ea98589d0eadb1db5..fb5a9ffc08ec654117a38d531e08fe788f9cb418 100644
--- a/third_party/WebKit/LayoutTests/scrollbars/listbox-scrollbar-combinations.html
+++ b/third_party/WebKit/LayoutTests/scrollbars/listbox-scrollbar-combinations.html
@@ -287,6 +287,8 @@ option[selected] {
     border-color: transparent;
     border-width: 13px 0;
     min-height: 20px;
+    border-style: solid;

[Timothy Loh, 2015/11/24 00:10:00]

I don't think this will inherit to :hover and so on, so you'll have to update
those too

[Savago, 2015/11/24 00:42:52]

It does (i.e. the scrollbars will have rounded border when there is a mouse
hover).

+    border-color: white;
 }
 
 ::-webkit-scrollbar-thumb:vertical:hover {
@@ -339,6 +341,8 @@ option[selected] {
     -webkit-border-image: url(resources/vertical-track-disabled.png) 13 0 13 0;
     border-color: transparent;
     border-width: 13px 0;
+    border-style: solid;
+    border-color: white;
 }
 
 ::-webkit-scrollbar-track-piece:vertical:decrement {