Improve documentation for custome token.

Bug: 37963830
Test: none
Change-Id: I1ca14d0b5e0779ae96c867806ddcc6792621876f
diff --git a/core/java/android/accounts/AccountManager.java b/core/java/android/accounts/AccountManager.java
index a446296..a209d28 100644
--- a/core/java/android/accounts/AccountManager.java
+++ b/core/java/android/accounts/AccountManager.java
@@ -242,10 +242,13 @@
     public static final String KEY_LAST_AUTHENTICATED_TIME = "lastAuthenticatedTime";
 
     /**
-     * Authenticators using 'customTokens' option will also get the UID of the
-     * caller
+     * The UID of caller app.
      */
     public static final String KEY_CALLER_UID = "callerUid";
+
+    /**
+     * The process id of caller app.
+     */
     public static final String KEY_CALLER_PID = "callerPid";
 
     /**