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 0462a03563e61ac78938614b40fc1fcaac5d483e..917d498a8ea21cb520c28906226b9fb5220d3a05 100644
--- a/ui/message_center/message_center.cc
+++ b/ui/message_center/message_center.cc
@@ -94,6 +94,12 @@ void MessageCenter::SetNotificationSecondaryIcon(const std::string& id,
     NotifyMessageCenterChanged(true);
 }
 
+void MessageCenter::SetNotificationImage(const std::string& id,
+                                         const gfx::ImageSkia& image) {
+  if (notification_list_->SetNotificationImage(id, image))
+    NotifyMessageCenterChanged(true);
+}
+
 //------------------------------------------------------------------------------
 // Overridden from NotificationList::Delegate.