DO NOT MERGE: add interim startDream api. am: 93e654d66c

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/19901885

Change-Id: I9a71dac740cb498ed64aaecf2e6c7556bf6fc57e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>