telemetry_unittests failing on chromium.mac/Mac10.9 Tests (dbg)

Builders failed on: 
- Mac10.9 Tests (dbg): 
  https://build.chromium.org/p/chromium.mac/builders/Mac10.9%20Tests%20%28dbg%29

We've begun seeing timeouts on the Mac bots of telemetry_unittests. Nothing in the logs strikes me, and they are flaky timeouts.

Example failures:
https://uberchromegw.corp.google.com/i/chromium.mac/builders/Mac10.9%20Tests%20%28dbg%29/builds/46264

https://uberchromegw.corp.google.com/i/chromium.mac/builders/Mac10.9%20Tests%20%28dbg%29/builds/46275

Suspected CL range: https://chromium.googlesource.com/chromium/src/+log/e6cd028398de42ee935518fc21e14b92b2f9812f%5E..83b895e9136947f824c9e7b5f728d193851730b6?pretty=fuller&n=

nednguyen@ could you help triage this?