Merge "GpuService: add RootTargetPreparer to gpuservice_unittest" am: ced64f0280 am: 6b31f7bd91 am: 94cad7a5af

Original change: https://android-review.googlesource.com/c/platform/frameworks/native/+/1475436

Change-Id: I4edf2950e45a1eb0755938072b5b8a99099d9661