Only start tracing in the next frame

In order to match tracing markers with the metrics, we should start
the tracing marker at the beginning of the next frame, as this is
also the point in time where we start counting janky frames.

Test: Take trace, inspect
Bug: 185902609
Change-Id: I2ec70b3fc2d3236bc24891ef698fdd7ac2917b01
2 files changed