Background context: go/memory-infra

After fix in issue 726393, we no longer have periodic triggers enabled by default. The UI should pass the right triggers for tracing. In the current setup for desktop, tracing_ui.cc sets the periodic triggers for memory-infra. This does not work on Android because the inspect?tracing UI uses devtools api to start tracing which does not use the tracing ui to start and stop tracing. So, thw inspect UI should take care of passing right triggers.

prototype cl: https://codereview.chromium.org/2933193002/