Implement permission granting in clipboard.

Change-Id: I9a7a949d1aaf4b3beabceaf807fb7d3b040e4ea8
diff --git a/services/java/com/android/server/am/UriPermissionOwner.java b/services/java/com/android/server/am/UriPermissionOwner.java
index 99c82e6..68a2e0f 100644
--- a/services/java/com/android/server/am/UriPermissionOwner.java
+++ b/services/java/com/android/server/am/UriPermissionOwner.java
@@ -45,7 +45,7 @@
     }
 
     Binder getExternalTokenLocked() {
-        if (externalToken != null) {
+        if (externalToken == null) {
             externalToken = new ExternalToken();
         }
         return externalToken;