This is the meta bug for moving Telemetry to Chromium/src. The rationales are:
1) Most of the known customers of Telemetry are benchmarks & tests in chromium/src/. Putting Telemetry in Catapult repo slow down the development cycle as API updates require 3/4 sided patches and devs sometimes need to wait for the roll to know they broke tests (e.g:  issue 886913 ).
2) For clients that want benchmark which are not in Chromium/src, they either don't need Telemetry or there are other ways to get Telemetry:
  i) If they want performance benchmark for web development, lighthouse (https://developers.google.com/web/tools/lighthouse/) is the recommended framework. Notes that making Telemetry a perf test framework for webdevs was the original reason why we moved Telemetry to catapult and that vision is now fulfilled by LightHouse.

  ii) If they still want Telemetry for benchmarking, they can use Telemetry isolate through running: python tools/mb/mb.py zip out/Release telemetry_gpu_integration_test_scripts_only out/my_scripts.zip


Few more details still need to be fleshed out for this bug:
1) What to do about Telemetry's deps like vinn/ or devil/ ?
2) What is our testing look like? Should we add telemetry_unittest_references to Chromium CQ to ensure we don't lose Telemetry ref build coverage?