only use glReadPixels() when needed when taking screenshots

some drivers don't support this yet, so we use a system
property to enable the glReadPixels "workaround" for them:

  ro.bq.gpu_to_cpu_unsupported=1

Change-Id: I74d6a3a8f0cee8d5a507b72c760cf247e39195e0
2 files changed