By keeping track of the stack of counters we can properly subtract the
subcounter times and properly measure the own-time spent in each runtime
function. This is useful to get more details for builtins like HandleApiCall
which are typical top-level entries for chome which previously prevent
measurements of sub-calls to builtins/runtime functions.

BUG=

Review URL: https://codereview.chromium.org/1681943002

Cr-Commit-Position: refs/heads/master@{#33901}