Update TrustAgentService API after review.

Also documents timebase on related DevicePolicyManager API.

Fixes bugs 16401527 and 17046034

Change-Id: I8ee6d0055ab6f52ec71630344d3232f7875d9c1d
diff --git a/core/java/android/app/admin/DevicePolicyManager.java b/core/java/android/app/admin/DevicePolicyManager.java
index 0dc8f66..41bbb87 100644
--- a/core/java/android/app/admin/DevicePolicyManager.java
+++ b/core/java/android/app/admin/DevicePolicyManager.java
@@ -1373,6 +1373,8 @@
      * and its profiles or a particular one.
      * @param admin The name of the admin component to check, or null to aggregate
      * all admins.
+     * @return time in milliseconds for the given admin or the minimum value (strictest) of
+     * all admins if admin is null.
      */
     public long getMaximumTimeToLock(ComponentName admin) {
         return getMaximumTimeToLock(admin, UserHandle.myUserId());