mash: Cleanly exit on SIGTERM, SIGINT, SIGHUP

chrome/app/BUILD.gn

Index: chrome/app/BUILD.gn
diff --git a/chrome/app/BUILD.gn b/chrome/app/BUILD.gn
index 010ecb459d630912220815265d61680837f34bc8..77d4efe999fc53bc9d0155dbf917dd572d139f42 100644
--- a/chrome/app/BUILD.gn
+++ b/chrome/app/BUILD.gn
@@ -17,6 +17,18 @@ source_set("command_ids") {
   ]
 }
 
+# Shared by //chrome/browser and //chrome/app/mash. Not in //chrome/common
+# because it isn't shared with processes like renderer, utility, etc.

[James Cook, 2017/03/01 18:24:38]

I ran this by sky@ -- there's not a great place for this code to live, but this
seems like the least bad.

+source_set("shutdown_signal_handlers") {
+  sources = [
+    "shutdown_signal_handlers_posix.cc",
+    "shutdown_signal_handlers_posix.h",
+  ]
+  deps = [
+    "//base",
+  ]
+}
+
 # On Windows, links chrome_dll.rc. On other platforms, does nothing so you can
 # unconditionally depend on it.
 source_set("chrome_dll_resources") {