ChromeOS OOBE: display icons specific to screen DPI.

chrome/browser/resources/chromeos/login/hd-iron-icon.css

Index: chrome/browser/resources/chromeos/login/hd-iron-icon.css
diff --git a/chrome/browser/resources/chromeos/login/hd-iron-icon.css b/chrome/browser/resources/chromeos/login/hd-iron-icon.css
new file mode 100644
index 0000000000000000000000000000000000000000..14dc6672383f2239c55f6037b906f147843dccf4
--- /dev/null
+++ b/chrome/browser/resources/chromeos/login/hd-iron-icon.css
@@ -0,0 +1,15 @@
+/* Copyright 2016 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. */
+
+@media all and (-webkit-max-device-pixel-ratio: 1.5) {
+  #icon2x {
+    display: none;
+  }
+}
+
+@media all and (-webkit-min-device-pixel-ratio: 1.5) {
+  #icon1x {
+    display: none;
+  }
+}