Add pre-send update support to DeferredUpdates

* PRESEND/POSTSEND constants can now be used in addUpdate()
  and addCallableUpdate() to control when the update runs.
  This is useful for updates that may report errors the client
  should see or to just get a head start on queued or pubsub
  based updates like CDN purges. The OutputPage::output() method
  can easily take a few 100ms.
* Removed some argument b/c code from doUpdates().
* Also moved DeferrableUpdate to a separate file.

Change-Id: I9831fe890f9f68f9ad8c4f4bba6921a8f29ba666

1 files changed, 14 insertions, 0 deletions

diff --git a/includes/deferred/DeferrableUpdate.php b/includes/deferred/DeferrableUpdate.php
new file mode 100644
index 000000000000..5f4d821060f0
--- /dev/null
+++ b/includes/deferred/DeferrableUpdate.php
@@ -0,0 +1,14 @@
+<?php
+
+/**
+ * Interface that deferrable updates should implement. Basically required so we
+ * can validate input on DeferredUpdates::addUpdate()
+ *
+ * @since 1.19
+ */
+interface DeferrableUpdate {
+	/**
+	 * Perform the actual work
+	 */
+	function doUpdate();
+}