WebUI: Fix md-select disabled look after adding left/right padding.

ui/webui/resources/html/md_select_css.html

Index: ui/webui/resources/html/md_select_css.html
diff --git a/ui/webui/resources/html/md_select_css.html b/ui/webui/resources/html/md_select_css.html
index 0c483beffdd2ad6b7a9946b6138db8d86d210800..f9a8062ca2d57c38ec145e4f78e55e138ca1f4b4 100644
--- a/ui/webui/resources/html/md_select_css.html
+++ b/ui/webui/resources/html/md_select_css.html
@@ -34,10 +34,13 @@
 
       /* Mirroring paper-dropdown-menu disabled style. */
       .md-select[disabled] {
-        border-bottom: 1px dashed var(--secondary-text-color);
+        pointer-events: none;
+      }
+
+      .md-select[disabled],
+      .md-select[disabled] + .md-select-underline {
         color: var(--secondary-text-color);
         opacity: 0.65;
-        pointer-events: none;
       }
 
       :host-context([dir=rtl]) .md-select {
@@ -77,6 +80,10 @@
         transition: transform 200ms ease-out;
       }
 
+      .md-select[disabled] + .md-select-underline {
+        border-top: 1px dashed var(--secondary-text-color);
+      }
+
       .md-select-wrapper {
         display: inline-block;
         max-width: 100%;