Fix test app to ensure that we destroy our GPU resources.

The problem arises on devices like the Nexus 10 where we allow the
destruction of resources using the destructor of a static variable.
However, we have no guarentee that the GPU driver has not already
cleaned up it's resources prior to our static destructor.

Review URL: https://codereview.appspot.com/6851124

git-svn-id: http://skia.googlecode.com/svn/trunk@6599 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed