Introduce lock screen app context to extension features

extensions/browser/process_map.h

Index: extensions/browser/process_map.h
diff --git a/extensions/browser/process_map.h b/extensions/browser/process_map.h
index ed28a5272d3239ac7d78121e2482cdfa707564a2..38bfc71a3a854e833099f73ae28e4c657e2652d0 100644
--- a/extensions/browser/process_map.h
+++ b/extensions/browser/process_map.h
@@ -116,6 +116,8 @@ class ProcessMap : public KeyedService {
   //
   // Anyhow, the expected behaviour is:
   //   - For hosted app processes, this will be blessed_web_page.
+  //   - For processes of platform apps running on lock screen, this will be
+  //     lock_screen_extension.
   //   - For other extension processes, this will be blessed_extension.
   //   - For WebUI processes, this will be a webui.
   //   - For any other extension we have the choice of unblessed_extension or