Add simple profiler wrapper

Converts V8 profiler objects into *.cpuprofile JSON structures suitable for
loading into Chrome or converting to calltree format to use with KCachegrind.

This is a temporary module, should be either contributed upstream or moved to
a separate npm module.

See the comment for usage instructions.

Change-Id: I6d260cbfa0e9a189341d9a6a9503f30cda78e621
Merge "Add simple profiler wrapper"