[scheduler] Remove implicit fallthrough in switch

Bail out early when a condition in the switch is fulfilled.
This does not change behaviour due to RemoveTaskObserver being no-op when
the task observer is not present in the list.

R=thakis@chromium.org

Bug: 177475
Change-Id: Ibc7772c79f8a8c8a1d63a997dabe1efda5d3a7bd
Reviewed-on: https://chromium-review.googlesource.com/891187
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532649}
void RendererSchedulerImpl::CreateTraceEventObjectSnapshot() const {
  TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler.debug"),
      "RendererScheduler", this, AsValue(helper_.NowTicks()));
}

void RendererSchedulerImpl::CreateTraceEventObjectSnapshot() const {
  TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler.debug"),
      "RendererScheduler", this, AsValue(helper_.NowTicks()));
}
