Adds a small icon to notifications, and connects it to synced notifications.

ui/message_center/notification.h

Index: ui/message_center/notification.h
diff --git a/ui/message_center/notification.h b/ui/message_center/notification.h
index 2e151b32f42d91e872fcc4231fe9a37085d0e1d1..ded9424153c55d5802bb83408cced9933f0f2679 100644
--- a/ui/message_center/notification.h
+++ b/ui/message_center/notification.h
@@ -45,6 +45,7 @@ class MESSAGE_CENTER_EXPORT RichNotificationData {
   base::string16 expanded_message;
   base::string16 context_message;
   gfx::Image image;
+  gfx::Image small_image;
   std::vector<NotificationItem> items;
   int progress;
   std::vector<ButtonInfo> buttons;
@@ -133,6 +134,11 @@ class MESSAGE_CENTER_EXPORT Notification {
   const gfx::Image& image() const { return optional_fields_.image; }
   void set_image(const gfx::Image& image) { optional_fields_.image = image; }
 
+  const gfx::Image& small_image() const { return optional_fields_.small_image; }
+  void set_small_image(const gfx::Image& image) {
+    optional_fields_.small_image = image;
+  }
+
   // Buttons, with icons fetched asynchronously.
   const std::vector<ButtonInfo>& buttons() const {
     return optional_fields_.buttons;