Extend flags passed to Trace::Start to also specify the clock source am: fbf4bd2f8d am: 26c80a8e1b am: c4afa1ca47

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

Change-Id: If74f78346e375912754777ac1b72c088e894a585
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>