Remove Notification::small_image_url_ as it has no users.

chrome/browser/notifications/message_center_notification_manager.cc

Index: chrome/browser/notifications/message_center_notification_manager.cc
diff --git a/chrome/browser/notifications/message_center_notification_manager.cc b/chrome/browser/notifications/message_center_notification_manager.cc
index 28c5f795178c2f9ee2a680958fdadc54a4e88240..ed495036cdeb435a9b173531a2c8b7936bb18b5e 100644
--- a/chrome/browser/notifications/message_center_notification_manager.cc
+++ b/chrome/browser/notifications/message_center_notification_manager.cc
@@ -408,7 +408,7 @@ void MessageCenterNotificationManager::ImageDownloads::StartDownloadWithImage(
   if (url.is_empty())
     return;
 
-  content::WebContents* contents = notification.GetWebContents();
+  content::WebContents* contents = notification.delegate()->GetWebContents();
   if (!contents) {
     LOG(WARNING) << "Notification needs an image but has no WebContents";
     return;
@@ -479,7 +479,7 @@ void MessageCenterNotificationManager::ProfileNotification::StartDownloads() {
 
 void
 MessageCenterNotificationManager::ProfileNotification::OnDownloadsCompleted() {
-  notification_.DoneRendering();
+  notification_.delegate()->ReleaseRenderViewHost();
 }
 
 void