The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f9e13a5cfe2f704ceec345a0210ff538343c496f

commit f9e13a5cfe2f704ceec345a0210ff538343c496f
Author: Etienne Bergeron <etienneb@chromium.org>
Date: Thu Sep 07 05:39:07 2017

Add renderers uptime metric to UKM reports.

This CL is adding the uptime for the renderers.

R=erikchen@chromium.org

Bug:  757869 
Change-Id: I911cbe6a3682b09968fe145ff32e5680aa9b4e4c
Reviewed-on: https://chromium-review.googlesource.com/626356
Commit-Queue: Erik Chen <erikchen@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#500227}
[modify] https://crrev.com/f9e13a5cfe2f704ceec345a0210ff538343c496f/chrome/browser/metrics/process_memory_metrics_emitter.cc
[modify] https://crrev.com/f9e13a5cfe2f704ceec345a0210ff538343c496f/chrome/browser/metrics/process_memory_metrics_emitter_browsertest.cc
[modify] https://crrev.com/f9e13a5cfe2f704ceec345a0210ff538343c496f/chrome/browser/metrics/process_memory_metrics_emitter_unittest.cc
[modify] https://crrev.com/f9e13a5cfe2f704ceec345a0210ff538343c496f/chrome/browser/metrics/renderer_uptime_tracker.cc
[modify] https://crrev.com/f9e13a5cfe2f704ceec345a0210ff538343c496f/chrome/browser/metrics/renderer_uptime_tracker.h
[modify] https://crrev.com/f9e13a5cfe2f704ceec345a0210ff538343c496f/tools/metrics/ukm/ukm.xml

We also need instrumentation for non-renderer processes. I think the easiest way to do this is to record time of creation of CU for each process, and to start creating CUs for non-renderer processes. e.g. see https://bugs.chromium.org/p/chromium/issues/detail?id=757873#c2.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/05d62532c8f1547464030cf32ba502e0f8429005

commit 05d62532c8f1547464030cf32ba502e0f8429005
Author: Etienne Bergeron <etienneb@chromium.org>
Date: Fri Oct 13 18:24:00 2017

Add memory_instrumentation UKMs for process uptime

This CL is adding the process uptime to UKM for the Browser process,
GPU process and for the renderers.

R=erikchen@chromium.org

Bug:  757869 
Change-Id: I9d9d84f421a585f54ed34549267a470141a93b98
Reviewed-on: https://chromium-review.googlesource.com/699152
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: lpy <lpy@chromium.org>
Reviewed-by: Brett Wilson <brettw@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#508760}
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/BUILD.gn
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/chrome_content_browser_client.cc
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/metrics/process_memory_metrics_emitter.cc
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/metrics/process_memory_metrics_emitter.h
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/metrics/process_memory_metrics_emitter_browsertest.cc
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/metrics/process_memory_metrics_emitter_unittest.cc
[add] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/resource_coordinator/browser_child_process_watcher.cc
[add] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/resource_coordinator/browser_child_process_watcher.h
[add] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/resource_coordinator/chrome_browser_main_extra_parts_resource_coordinator.cc
[add] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/chrome/browser/resource_coordinator/chrome_browser_main_extra_parts_resource_coordinator.h
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/content/browser/renderer_host/render_process_host_impl.cc
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/services/resource_coordinator/coordination_unit/coordination_unit_introspector_impl.cc
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/services/resource_coordinator/public/interfaces/coordination_unit_introspector.mojom
[modify] https://crrev.com/05d62532c8f1547464030cf32ba502e0f8429005/services/resource_coordinator/public/interfaces/signals.mojom