updated vgl viewport to better handle object loading/unloading.

Change-Id: I02db48b2792c9692f58cc18ce9ad47738a3cbbfe
Code cleanup.

Change-Id: I93260e3f9d1011196ebf825d0625ec2b2884de14
Remove unnecessary comments.

Change-Id: If8693a7efbd7f5605ffbf7d5daef914c6e7ebd72