Add webui handler for promotions on Android NTP.

chrome/browser/resources/ntp_android/ntp_android.css

Index: chrome/browser/resources/ntp_android/ntp_android.css
diff --git a/chrome/browser/resources/ntp_android/ntp_android.css b/chrome/browser/resources/ntp_android/ntp_android.css
index 0245152507180d3e5f9e9b33d7cfa572d4496259..e2fcdc099d51486dd6afd2f65eb899483357ef0d 100644
--- a/chrome/browser/resources/ntp_android/ntp_android.css
+++ b/chrome/browser/resources/ntp_android/ntp_android.css
@@ -37,14 +37,36 @@ body {
   width: 275px;
 }
 
+.promo-action-target {
+  -webkit-tap-highlight-color: transparent;
+}
+
 .promo-message {
   font-family: Arial, sans-serif;
-  font-size: 14pt;
-  margin-bottom: 16px;
-  margin-top: 16px;
+  font-size: 12pt;
+  margin: 16px 24px;
+  text-align: center;
+}
+
+.promo-button {
+  background: -webkit-gradient(
+      linear, left top, left bottom, from(#f5f5f5), to(#f1f1f1));
+  border: 1px solid #ccc;
+  border-radius: 5px;
+  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.08),
+      inset 0 0 2px rgba(255, 255, 255, 0.6);
+  font-size: 12pt;
+  margin-left: auto;
+  margin-right: auto;
+  padding: 10px;
   text-align: center;
 }
 
+.promo-button-active {
+  -webkit-tap-highlight-color: transparent;
+  background: rgba(51, 181, 229, 0.4);
+}
+
 .promo-sync-graphic {
   background-image: url(images/syncfographic_mdpi.png);
   background-repeat: no-repeat;