DevTools: "JS sampling" checkbox should not affect recorded profile

The checkbos now affects only the next recorded profile. Presentation of the existing one does not change.

BUG=426149

Review URL: https://codereview.chromium.org/695843002

git-svn-id: svn://svn.chromium.org/blink/trunk@184734 bbb929c8-8fbe-4397-9dbb-9b2b20218538