Currently, whether test APKs are downloaded for VR and AR is controlled by the environment variable DOWNLOAD_VR_TEST_APKS, read by src/third_party/gvr-android-sdk/test-apks/update.py and src/third_party/arcore-android-sdk/test-apks/update.py. Environment variables make it harder to find dead code and perform cleanups and gclient variables allow for making this decision at a higher level.