[automerger skipped] tracinglib: update README, fix tracing demos am: 8cfb03b7 am: df14f688 -s ours

am skip reason: Merged-In I72d95ccc7e5aeb09662eea3249e5f46ad8cdf995 with SHA-1 aca8680d is already in history

Original change: https://android-review.googlesource.com/c/platform/frameworks/libs/systemui/+/3326138



Change-Id: Iae3fb99823d61f04a2fe94e2cd28b5984f2aa717
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>