update_engine: Share payloads for a maximum of five days only.

This helps limit exposure of what version the device may or may not be
running.

BUG=chromium:424823
TEST=New unit test + unit tests pass.

Change-Id: I9db6f8d560e359c2b8a65d1381dc44320ed4b3a1
Reviewed-on: https://chromium-review.googlesource.com/227592
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Tested-by: David Zeuthen <zeuthen@chromium.org>
Commit-Queue: David Zeuthen <zeuthen@chromium.org>
diff --git a/real_system_state.cc b/real_system_state.cc
index faac5cd..d61e8c3 100644
--- a/real_system_state.cc
+++ b/real_system_state.cc
@@ -41,8 +41,9 @@
     system_rebooted_ = true;
   }
 
-  p2p_manager_.reset(P2PManager::Construct(nullptr, &prefs_, "cros_au",
-                                           kMaxP2PFilesToKeep));
+  p2p_manager_.reset(P2PManager::Construct(
+      nullptr, &prefs_, &clock_, "cros_au", kMaxP2PFilesToKeep,
+      base::TimeDelta::FromDays(kMaxP2PFileAgeDays)));
 
   // Initialize the Update Manager using the default state factory.
   chromeos_update_manager::State* um_state =