UpdateEngineStable: document security difference am: 4aae5e1436

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2889550

Change-Id: I135da1733efd3c73dcddfa1db52321c036748358
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
diff --git a/stable/android/os/IUpdateEngineStable.aidl b/stable/android/os/IUpdateEngineStable.aidl
index b3b6674..5aa15ba 100644
--- a/stable/android/os/IUpdateEngineStable.aidl
+++ b/stable/android/os/IUpdateEngineStable.aidl
@@ -21,6 +21,10 @@
 
 /**
  * The stable interface exposed by the update engine daemon.
+ *
+ * WARNING: this interface exposes less capabilities than IUpdateEngine,
+ * for instance, not having a cancel method. This is relied on for
+ * security.
  */
 interface IUpdateEngineStable {
   /**