AU: Send UPDATE_AVAILABLE status.

We'll need a new status value to mean that an update is available but it's not
being applied. libcros/Chrome/OOBE currently assume that UPDATE_AVAILABLE will
transition to DOWNLOADING.

BUG=8155
TEST=unit test; tested on the device -- right after checking for updates the
UI transitions to "System update available..." which is incrementally better.

Change-Id: I59fff4a64a8947d8866b57bc22d3179ecfdb0140

Review URL: http://codereview.chromium.org/4171003
diff --git a/update_attempter.cc b/update_attempter.cc
index 5b7f988..f788ac8 100644
--- a/update_attempter.cc
+++ b/update_attempter.cc
@@ -344,6 +344,7 @@
     is_full_update_ = plan.is_full_update;
     SetupDownload();
     SetupPriorityManagement();
+    SetStatusAndNotify(UPDATE_STATUS_UPDATE_AVAILABLE);
   } else if (type == DownloadAction::StaticType()) {
     SetStatusAndNotify(UPDATE_STATUS_FINALIZING);
   }