MD Settings: long dialog body should have overscroll line.

ui/webui/resources/cr_elements/cr_dialog/cr_dialog.html

Index: ui/webui/resources/cr_elements/cr_dialog/cr_dialog.html
diff --git a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.html b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.html
index 2747f0e648fdf5e0b014fc00deb63a31e3300da5..14a5a866e2d4e464289772fb38d5256ff0eed063 100644
--- a/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.html
+++ b/ui/webui/resources/cr_elements/cr_dialog/cr_dialog.html
@@ -59,8 +59,17 @@
       .body-container {
         display: flex;
         flex-direction: column;
-        /* TODO(dbeam): copy <paper-dialog-scrollable>'s dividers? */
         overflow: auto;
+        @apply(--cr-dialog-body-container);
+      }
+
+      :host([show-scroll-borders]) .body-container {
+        /* Prevent layout moving when border does appear. */
+        border-bottom: 1px solid transparent;
+      }
+
+      :host([show-scroll-borders]) .body-container.bottom-scrollable {
+        border-bottom: 1px solid var(--paper-grey-300);
       }
 
       :host ::content .body {
@@ -110,6 +119,7 @@
     </div>
     <div class="body-container">
       <content select=".body"></content>
+      <span id="bodyBottomMarker"></span>
     </div>
     <content select=".button-container"></content>
     <content select=".footer"></content>