minor recovery changes

- add the --just_exit option to make recovery exit normally without doing anything
- make it possible to build updater extensions in C++
- add the clear_display command so that the updater binary can request
  recovery switch to the NONE background UI

These are all used to support the notion of using OTA as a factory
reflash mechanism.

Change-Id: Ib00d1cbf540feff38f52a61a2cf198915b48488c

1 files changed, 2 insertions, 0 deletions

diff --git a/install.cpp b/install.cpp
index 0783433..4d73aa9 100644
--- a/install.cpp
+++ b/install.cpp
@@ -156,6 +156,8 @@ try_update_binary(const char *path, ZipArchive *zip, int* wipe_cache) {
             }
         } else if (strcmp(command, "wipe_cache") == 0) {
             *wipe_cache = 1;
+        } else if (strcmp(command, "clear_display") == 0) {
+            ui->SetBackground(RecoveryUI::NONE);
         } else {
             LOGE("unknown command [%s]\n", command);
         }