There are TODOs for all of these in the code base. This pertains to 
chrome/browser/profiling_host/background_profiling_triggers_unittest.cc
  - RendererSampling mode

chrome/browser/profiling_host/memlog_browsertest.cc
  - RendererSampling mode
  - GPU profiling verification
  - Process crash robustness.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bd5bd90ca753c5faed4e755d361754fa75195176

commit bd5bd90ca753c5faed4e755d361754fa75195176
Author: Albert J. Wong <ajwong@chromium.org>
Date: Thu Nov 09 19:56:15 2017

Reland: OOPHP:Add 3 new modes of process profiling

Original CL: https://chromium-review.googlesource.com/742227

Renderer Sampling mode was causing tests to be non-deterministic. This
adds an override method that test can use to make the sampling be 100%
which is deterministic.

Bug:  780955 ,  777984 
Change-Id: I239654ebd41fc51227b257525008f62322ff8318
TBR: brettw,erikchen
Reviewed-on: https://chromium-review.googlesource.com/758490
Commit-Queue: Albert J. Wong <ajwong@chromium.org>
Reviewed-by: Albert J. Wong <ajwong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515252}
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/about_flags.cc
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/flag_descriptions.cc
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/flag_descriptions.h
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/profiling_host/background_profiling_triggers.cc
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/profiling_host/background_profiling_triggers.h
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/profiling_host/background_profiling_triggers_unittest.cc
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/profiling_host/memlog_browsertest.cc
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/profiling_host/profiling_process_host.cc
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/profiling_host/profiling_process_host.h
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/browser/ui/webui/memory_internals_ui.cc
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/common/chrome_switches.cc
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/common/chrome_switches.h
[modify] https://crrev.com/bd5bd90ca753c5faed4e755d361754fa75195176/chrome/profiling/memlog_connection_manager.cc

We have e2e tests that verify GPU and renderer profiling. We have unit tests that confirm that timeouts in the profiling service are dealt with appropriately: https://cs.chromium.org/chromium/src/chrome/common/profiling/memlog_sender_pipe_unittest.cc?type=cs&q=memlog_.*test&sq=package:chromium&l=60. Crashes are less of a concern - they cause pipe write/read error, which is handled gracefully.