[EasyUnlock] Force user to enter their password after 20 hours.

components/proximity_auth/proximity_auth_pref_names.cc

Index: components/proximity_auth/proximity_auth_pref_names.cc
diff --git a/components/proximity_auth/proximity_auth_pref_names.cc b/components/proximity_auth/proximity_auth_pref_names.cc
index 13d9fa1db34f8048bfc667a339693f046299fc09..3e0267e687de19f6d421c780f9785f049430fbb1 100644
--- a/components/proximity_auth/proximity_auth_pref_names.cc
+++ b/components/proximity_auth/proximity_auth_pref_names.cc
@@ -7,6 +7,11 @@
 namespace proximity_auth {
 namespace prefs {
 
+// The timestamp of the last password entry in milliseconds, used to enforce
+// reauthing with the password after a given time period has elapsed.
+const char kProximityAuthLastPasswordEntryTimestampMs[] =
+    "proximity_auth.last_password_entry_timestamp_ms";
+
 // The dictionary containing remote BLE devices.
 const char kProximityAuthRemoteBleDevices[] =
     "proximity_auth.remote_ble_devices";