Extend flags passed to Trace::Start to also specify the clock source am: fbf4bd2f8d am: 26c80a8e1b

Original change: https://android-review.googlesource.com/c/platform/art/+/2392999

Change-Id: Ib323cf803ce008edf89266c47715d26b083dae7e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>