Magnifier Material Polish

[Cameron-Micka]

The magnifier shader now supports rounded corners. Updated the sample too:

(Also found and fixed a small include bug in the acrylic shader.)

Verification

As a reviewer, it is possible to check out this change locally by using the following
commands (substituting {PR_ID} with the ID of this pull request):

git fetch origin pull/{PR_ID}/head:name_of_local_branch

git checkout name_of_local_branch