Overscan calibration UI.

chrome/browser/resources/options/chromeos/display_options.css

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file. */
 
 #display-options-page {
   background-color: rgb(240, 240, 240);
 }
 
 #display-options-content-area {
   padding: 0;
@@ skipping 84 matching lines @@
   color: rgb(0, 138, 255);
 }
 
 .display-options-single-button-container {
   margin: 5px 0 5px 0;
 }
 
 .display-options-button {
   width: 120px;
 }
+
+#display-overscan-calibration-arrow-container {
+  background: transparent;
+  border: none;
+  position: absolute;
+  z-index: 3;
+}
+
+/* The small arrows to denote the overscan calibration mode.  The triangular
+ * arrows are achieved by css border. */
+.display-overscan-calibration-arrow {
+  border: 10px solid transparent;
+  height: 0;
+  position: absolute;
+  width: 0;
+}
+
+.display-overscan-arrow-to-top {
+  border-bottom-color: rgb(64, 64, 64);
+}
+
+.display-overscan-arrow-to-left {
+  border-right-color: rgb(64, 64, 64);
+}
+
+.display-overscan-arrow-to-bottom {
+  border-top-color: rgb(64, 64, 64);
+}
+
+.display-overscan-arrow-to-right {
+  border-left-color: rgb(64, 64, 64);
+}