Previously embedder had to create an instance of TracingCpuProfiler explicitly.
The patch makes the profiler created automatically for every isolate.
The profiler has no overhead unless tracing with v8.cpu_profiler category is enabled.

Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I9369c2c56bcddc72093eda33dc2bc185c9253b4a
Reviewed-on: https://chromium-review.googlesource.com/1006049
Commit-Queue: Alexei Filippov <alph@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52552}