[timeline] Add  support for timeline asynchronous events in android platform trace
[timeline] Add  support for timeline asynchronous events in android platform trace

systrace don't support async timeline events, when define sync event can
show in timeline, but not including systrace.
more details, see https://github.com/dart-lang/sdk/issues/39726

Bug:https://github.com/dart-lang/sdk/issues/39726
Change-Id: Iea705f7a4f67e540411ef2cb81ccff9b3b793b31
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/127920
Commit-Queue: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@google.com>
Reviewed-by: Ryan Macnak <d738b7f001baf9789095d7dc549cff6de60b011d@google.com>

dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk