config_service: make UI responsive and change colors.

appengine/config_service/ui/common/auth-signin.html

 <!--
   Copyright 2017 The LUCI Authors. All rights reserved.
   Use of this source code is governed under the Apache License, Version 2.0
   that can be found in the LICENSE file.
 
   The `auth-signin` element displays sign-in/sign-out button, user email and
   avatar.
   It has a google-signin/google-signin-aware element under the hood that handles
   the actual OAuth logic.
 
@@ skipping 20 matching lines @@
 <link rel="import" href="../../bower_components/polymer/polymer.html">
 
 
 <dom-module id="auth-signin">
   <template>
     <style>
       #avatar { border-radius: 5px; }
 
       .center { vertical-align: middle; }
 
-      .typeface { font-size: 75%; }
+      .typeface { 
+        font-size: 75%;
+        color: white;
+      }
     </style>
 
     <google-signin-aware id="aware"
       client-id="[[client_id]]"
       scopes="email"
       on-google-signin-aware-success="_onSignin"
       on-google-signin-aware-signed-out="_onSignout">
     </google-signin-aware>
 
     <template is="dom-if" if="[[!signed_in]]">
@@ skipping 109 matching lines @@
         this.$.aware.signIn();
       },
 
       signOut: function() {
         this.$.aware.signOut();
         window.location.reload();
       }
     });
   </script>
 </dom-module>