Added support for image notifications.

ui/message_center/message_center.cc

Index: ui/message_center/message_center.cc
diff --git a/ui/message_center/message_center.cc b/ui/message_center/message_center.cc
index a5460ee89f424a57417277f9c91e2db8d5a32f4b..2110c154ebdb4c0820759807427d8033e5ca8313 100644
--- a/ui/message_center/message_center.cc
+++ b/ui/message_center/message_center.cc
@@ -89,6 +89,12 @@ void MessageCenter::SetNotificationSecondaryIcon(const std::string& id,
     host_->MessageCenterChanged(true);
 }
 
+void MessageCenter::SetNotificationImage(const std::string& id,
+                                         const gfx::ImageSkia& image) {
+  if (notification_list_->SetNotificationImage(id, image) && host_)
+    host_->MessageCenterChanged(true);
+}
+
 //------------------------------------------------------------------------------
 // Overridden from NotificationList::Delegate.