Do not create a CPU profiler for each isolate implicitly.

BUG=v8:7070

Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I6ddd93c58f56591477d8fe4249103a74b7698904
Reviewed-on: https://chromium-review.googlesource.com/1043449
Commit-Queue: Alexei Filippov <alph@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53449}