By default activities cannot be embedded by non-privileged
processes. Apps can either declare their activities to be available
for untrusted embedding, or limit it to certain trusted hosts.
This CL verifies that an application cannot embed activities that
didn't opt in, and verifies that in untrusted mode the host cannot
request SurfaceControl transactions or position the embedded
container outside of the task bounds.
Bug: 197364677
Test: ActivityEmbeddingCrossUidTests, TaskFragmentOrganizerTest
Change-Id: Ief54c9acae1a9a4152af710f67e7810afdcff9ba
97b59a72fa