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

chrome/browser/resources/contextual_search/promo.css

 /* Copyright 2014 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. */
 
-/* TODO: Need to clean up @font-face after we remove font-family from body. */
-@font-face {
-  font-family: 'Roboto2';
-  font-weight: 400;
-  src: local('Roboto'), local('Roboto2-Regular'),
-      url(chrome://resources/roboto/roboto.woff2) format('woff2'),
-      url(chrome://resources/roboto/roboto.woff) format('woff');
-}
-
 /* TODO(pedrosimonetti): Find a better way to fix the problem when the
  * text scaling preference is set to a high value.
  *
  * This CSS rule prevents the promo text from scaling as explained here:
  * https://code.google.com/p/chromium/issues/detail?id=252828#c10
  *
  * For for background about the problem, see:
  * https://code.google.com/p/chromium/issues/detail?id=466773
  */
 #heading,
 #description {
   max-height: 999999px;
 }
 
 body {
-  font-family: 'Roboto2', sans-serif;
+  font-family: 'Roboto', sans-serif;
   margin: 0;
 }
 
 a {
   text-decoration: none;
 }
 
 a.colored-link {
   color: rgb(66, 133, 244);
 }
@@ skipping 85 matching lines @@
   }
   html[dir='rtl'] .landscape {
     float: right;
   }
 }
 
 button {
   background: none;
   border: none;
   display: inline-block;
-  font-family: 'Roboto2', sans-serif;
+  font-family: 'Roboto', sans-serif;
   font-size: 14px;
   margin: 6px 0;
   /* We use a slightly different top-bottom padding because Roboto has a
    * rendering bug which makes an extra padding to be rendered at the bottom of
    * text.
    */
   padding: 12px 16px 8px;
   white-space: nowrap;
 }
 
 button .caption {
   text-transform: uppercase;
 }
 
 #optin-button {
   background: rgb(66, 133, 244);
   background-clip: padding-box;
   border-radius: 3px;
 }
 
 #optin-button .caption {
   color: white;
 }
 
 #optout-button .caption {
   color: rgb(66, 133, 244);
 }