AU: Catch terminate signals and block exit if necessary.
Adds a global Terminator class to manage signals and exit blocking.
BUG=7392
TEST=unit tests, gmerged on device, initctl stop update-engine
Change-Id: I2291d4eb55240a6662b18ff834af161d957bce2f
Review URL: http://codereview.chromium.org/3608015
diff --git a/SConstruct b/SConstruct
index c42b528..1a73466 100644
--- a/SConstruct
+++ b/SConstruct
@@ -264,6 +264,7 @@
split_file_writer.cc
subprocess.cc
tarjan.cc
+ terminator.cc
topological_sort.cc
update_attempter.cc
update_check_scheduler.cc