Add Roboto-Medium webfont and factor out common Roboto WebUI CSS file.

ui/webui/resources/css/roboto.css

Index: ui/webui/resources/css/roboto.css
diff --git a/ui/webui/resources/css/roboto.css b/ui/webui/resources/css/roboto.css
new file mode 100644
index 0000000000000000000000000000000000000000..776fa9289300b538fb2f8f87e593258cdb5ce489
--- /dev/null
+++ b/ui/webui/resources/css/roboto.css
@@ -0,0 +1,23 @@
+/* Copyright 2015 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. */
+
+@font-face {
+  font-family: 'Roboto';
+  font-style: normal;
+  font-weight: 400;
+  src: local('Roboto'), local('Roboto-Regular'),
+      url(chrome://resources/roboto/roboto-regular-latin.woff2) format('woff2');
+  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02C6, U+02DA, U+02DC,
+      U+2000-206F, U+2074, U+20AC, U+2212, U+2215, U+E0FF, U+EFFD, U+F000;
+}
+
+@font-face {
+  font-family: 'Roboto';
+  font-style: normal;
+  font-weight: 500;
+  src: local('Roboto Medium'), local('Roboto-Medium'),
+      url(chrome://resources/roboto/roboto-medium-latin.woff2) format('woff2');
+  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02C6, U+02DA, U+02DC,
+      U+2000-206F, U+2074, U+20AC, U+2212, U+2215, U+E0FF, U+EFFD, U+F000;
+}