Reduce TestProjectedHexahedra window size to 500x500.

The previous window size of 800x800 seemed needlessly large, and causes
test failures on screens with a height of 800 or less (e.g. some laptops).

Change-Id: Id6abd1bd773f0a074ebedb8eb0f699a7c8a665b5
Merge topic 'test-projected-hexahedra-size' into master

79feb9dd Reduce TestProjectedHexahedra window size to 500x500.