Merge "Adding optional block to run before screenshot" into udc-dev am: a6550a83 am: 3523cdac am: 15942c7f

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/23356977



Change-Id: I2bc9bdd8b7c75d5015fc069079c5807d0dfb7312
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>