src: fix v8::CpuProfiler idle sampling
src: fix v8::CpuProfiler idle sampling

Ensure that samples are evenly distributed, which is required for
v8::CpuProfiler users to work correctly (v8-profiler / node-inspector).

PR-URL: https://github.com/nodejs/node/pull/2324
Reviewed-By: Ben Noordhuis <59bd0a3ff43b32849b319e645d4798d8a5d1e889@bnoordhuis.nl>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node