Proper API hierarchy between MODULE_LIBS and PRIV_APPS system APIs

Test: build / treehugger
Bug: 146727827
Change-Id: Ie1ad6711c490c679ebcfacd97154380a8810ba1c
diff --git a/StubLibraries.bp b/StubLibraries.bp
index 56c5688..decbb85 100644
--- a/StubLibraries.bp
+++ b/StubLibraries.bp
@@ -155,6 +155,9 @@
 module_libs = " " +
     " --show-annotation android.annotation.SystemApi\\(" +
         "client=android.annotation.SystemApi.Client.MODULE_LIBRARIES" +
+    "\\)" +
+    " --show-for-stub-purposes-annotation android.annotation.SystemApi\\(" +
+        "client=android.annotation.SystemApi.Client.PRIVILEGED_APPS" +
     "\\) "
 
 droidstubs {
@@ -232,9 +235,8 @@
 }
 
 /////////////////////////////////////////////////////////////////////
-// Following droidstubs modules are for extra APIs for modules.
-// The framework currently have two more API surfaces for modules:
-// @SystemApi(client=MODULE_APPS) and @SystemApi(client=MODULE_LIBRARIES)
+// Following droidstubs modules are for extra APIs for modules,
+// namely @SystemApi(client=MODULE_LIBRARIES) APIs.
 /////////////////////////////////////////////////////////////////////
 
 // TODO(b/146727827) remove the *-api module when we can teach metalava