[9] Review request for JDK-8144789: Incorrect assertion fails in the GlassCursor.m

[Morris Meyer]

Vadim and Kevin,

Please review this fix for the GlassCursor.m assertion failure.

Thanks,

        --morris

WEBREV - http://cr.openjdk.java.net/~morris/JDK-8144780.01a
BUG - https://bugs.openjdk.java.net/browse/JDK-8144780