Work Challenge: Handle Recents launches

Intercept calls to start activities from the recents
stack and show the Work Challenge if needed. This requires
passing the taskId to ConfirmDeviceCredential so it can
launch the recents task itself when the credentials are
confirmed.

Change-Id: I013b134f3f31a35b551ad683c68cc89b8af44499
diff --git a/core/java/android/content/Intent.java b/core/java/android/content/Intent.java
index c3dfab4..35cd2be 100644
--- a/core/java/android/content/Intent.java
+++ b/core/java/android/content/Intent.java
@@ -3604,6 +3604,15 @@
     public static final String EXTRA_USER_ID = "android.intent.extra.USER_ID";
 
     /**
+     * An int representing the task id to be retrieved. This is used when a launch from recents is
+     * intercepted by another action such as credentials confirmation to remember which task should
+     * be resumed when complete.
+     *
+     * @hide
+     */
+    public static final String EXTRA_TASK_ID = "android.intent.extra.TASK_ID";
+
+    /**
      * An Intent[] describing additional, alternate choices you would like shown with
      * {@link #ACTION_CHOOSER}.
      *