https://codereview.chromium.org/2296243002/ introduced 2 minor bugs
related to the Reset scope.

The tracing version requires that we reset the counters everytime we
start a new top level trace event, unless the top level one is not
really a top level (i.e. has the right type but called in a nested way)

Bugs are:
1- Reseting was guarded behind a check for the runtime call stats
version only.
2- We never set that we are already inside a scope, so the nested
case would fail as well.

R=lpy@chromium.org, cbruni@chromium.org
BUG=642373

Review-Url: https://codereview.chromium.org/2311033002
Cr-Commit-Position: refs/heads/master@{#39214}