Add SingleLogSource to system_logs sources

chrome/browser/chromeos/BUILD.gn

Index: chrome/browser/chromeos/BUILD.gn
diff --git a/chrome/browser/chromeos/BUILD.gn b/chrome/browser/chromeos/BUILD.gn
index 2798fc4ec454fea268b8c4d874ab9537e9a94ce6..b2be99315e4d1c073f673945945b589dfcf85775 100644
--- a/chrome/browser/chromeos/BUILD.gn
+++ b/chrome/browser/chromeos/BUILD.gn
@@ -1360,6 +1360,8 @@ source_set("chromeos") {
     "system_logs/device_event_log_source.h",
     "system_logs/lsb_release_log_source.cc",
     "system_logs/lsb_release_log_source.h",
+    "system_logs/single_log_source.cc",
+    "system_logs/single_log_source.h",
     "system_logs/touch_log_source.h",
     "system_logs/touch_log_source_ozone.cc",
     "system_logs/touch_log_source_x11.cc",
@@ -1758,6 +1760,7 @@ source_set("unit_tests") {
     "status/data_promo_notification_unittest.cc",
     "system/automatic_reboot_manager_unittest.cc",
     "system/device_disabling_manager_unittest.cc",
+    "system_logs/single_log_source_unittest.cc",
     "tether/tether_service_unittest.cc",
     "ui/accessibility_focus_ring_controller_unittest.cc",
     "ui/idle_app_name_notification_view_unittest.cc",