Add chrome://proximity-auth UI implemented with Polymer.

components/proximity_auth/webui/resources/proximity_auth.css

Index: components/proximity_auth/webui/resources/proximity_auth.css
diff --git a/components/proximity_auth/webui/resources/proximity_auth.css b/components/proximity_auth/webui/resources/proximity_auth.css
index 25ecca35154bd0e8d2f43fdd5e3e9a0ff5da6237..40ad6c2ba01fb409b2eb9f1d1e4336bd5565646a 100644
--- a/components/proximity_auth/webui/resources/proximity_auth.css
+++ b/components/proximity_auth/webui/resources/proximity_auth.css
@@ -3,17 +3,24 @@
  * found in the LICENSE file.
  */
 
-html,
-body {
+@font-face {
+  font-family: 'Roboto2';
+  font-weight: 400;
+  src: local('Roboto'), local('Roboto2-Regular'),
+      url(../../../ui/webui/resources/roboto.woff2") format('woff2'),
+      url(../../../ui/webui/resources/roboto.woff") format('woff');
+}
+
+html, body {
   width: 100%;
   height: 100%;
   margin: 0;
   padding: 0;
   overflow: hidden;
+  font-family: 'Roboto2', sans-serif;
 }
 
-canvas {
-  width: 100%;
-  height: 100%;
-  margin: 0;
+#logs {
+  width: 40%;
+  border-left: 1px solid rgba(0,0,0,0.12);
 }