DO NOT MERGE: Cherry-pick 2ed524966d to JB.

This was contributed from AOSP, a fix to the management of URI write
permissions.  This is a very blatant bug, and with the new Intent ClipData
and other stuff we are making much more use of write permissions in JB,
so it is well worth taking.

Change-Id: I58c86119b4d5c13fefd090944bea139803df1a48

services/java/com/android/server/am/UriPermission.java

@@ -59,11 +59,11 @@ class UriPermission {
         if ((modeFlagsToClear&Intent.FLAG_GRANT_WRITE_URI_PERMISSION) != 0) {
             globalModeFlags &= ~Intent.FLAG_GRANT_WRITE_URI_PERMISSION;
             modeFlags &= ~Intent.FLAG_GRANT_WRITE_URI_PERMISSION;
-            if (readOwners.size() > 0) {
+            if (writeOwners.size() > 0) {
                 for (UriPermissionOwner r : writeOwners) {
                     r.removeWritePermission(this);
                 }
-                readOwners.clear();
+                writeOwners.clear();
             }
         }
     }