Friendly ping - what's the status here? Since the new metrics have already been adopted for heartbeats - I think it should be good to remove these now.

While I'm at it, a request from Mark:

"""
Can you please revise the "private" Memory histogram descriptions to mention they're emitted once per renderer (per UMA ping)?
"""

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/64b5560194a7a0eef4388a230528ab681a5e90a4

commit 64b5560194a7a0eef4388a230528ab681a5e90a4
Author: Mark Pearson <mpearson@chromium.org>
Date: Wed Nov 01 00:24:25 2017

Clarify Memory Histograms Emit Times

In many memory histograms, the last sentence is "Emitted once per UMA
ping."  But actually some subset of those are emitted multiple times,
one for each process.  In most of those cases, reading the rest of the
histogram description will make that clear.  In a few, it's not crystal
clear; one of them confused me for example.  I was going to simply
fix the more confusing ones, then simply decided that it's best to be
consistent.

This changelist adds "per process" to the last sentence as appropriate
on all memory histograms.

Bug:  765470 
Change-Id: Ia8187581381a13913f9eada5a1b0d82b8d1b3fbe
Reviewed-on: https://chromium-review.googlesource.com/747629
Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: Mark Pearson (busy Oct 31) <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513020}
[modify] https://crrev.com/64b5560194a7a0eef4388a230528ab681a5e90a4/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b8a68f222ccb9cdfc101af44919c30a5a84925ec

commit b8a68f222ccb9cdfc101af44919c30a5a84925ec
Author: Erik Chen <erikchen@chromium.org>
Date: Fri Nov 10 20:48:53 2017

Remove outdated memory metrics.

Metrics removed:
  Memory.Browser.Large2, Memory.RendererAll, Memory.Extension, Memory.Chrome,
  Memory.Renderer.Large2, Memory.Utility, Memory.Zygote, Memory.SandboxHelper,
  Memory.Gpu, Memory.PepperFlashPlugin, Memory.PepperPlugin,
  Memory.PepperPluginBroker, Memory.NativeClient, Memory.NativeClientBroker,
  Memory.Total2,

All of these metrics used ProcessMemoryInformation::working_set.priv, which
provided inconsistent numbers across platforms. Furthermore, on all platforms
but CrOS, this number included resident, but not swapped memory.

Not all of these metrics have replacements, but I've confirmed with all metric
owners that the metrics are no longer being looked at.

Bug:  765470 
Change-Id: I42cd3b2f680991c8a14e8606bda0aa7a1f36efdb
Reviewed-on: https://chromium-review.googlesource.com/756890
Commit-Queue: Erik Chen <erikchen@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Takashi Sakamoto <tasak@google.com>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Hajime Hoshi <hajimehoshi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515671}
[modify] https://crrev.com/b8a68f222ccb9cdfc101af44919c30a5a84925ec/chrome/browser/metrics/metrics_memory_details.cc
[modify] https://crrev.com/b8a68f222ccb9cdfc101af44919c30a5a84925ec/chrome/browser/metrics/metrics_memory_details_browsertest.cc
[modify] https://crrev.com/b8a68f222ccb9cdfc101af44919c30a5a84925ec/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/489b507f107f6faa1342b40f0fa90889fab58e05

commit 489b507f107f6faa1342b40f0fa90889fab58e05
Author: erikchen <erikchen@chromium.org>
Date: Fri Mar 09 16:53:34 2018

Remove unused memory metrics.

This CL removes several memory metrics that are not being used. These are:
  * Memory.{ProcessType}Count
  * Memory.*.Committed
  * Memory.Renderer{Shrink,Growth}In30Min
  * Memory.Swap.*

The memory metrics actively being used and developed are emitted in
ProcessMemoryMetricsEmitter. These are emitted in both UMA and UKM form. The UKM
form implicitly includes ProcessType, though with less granularity. Both the UMA
and UKMs include PrivateMemoryFootprint, a cross-platform consistent metric that
supercedes Memory.*.Committed. There is no replacement for
Memory.Renderer{Shrink,Growth}In30Min.

Bug:  765470 
Change-Id: I857f710eeb3ddf233b63be3139ea90ebe8d9a5c9
Reviewed-on: https://chromium-review.googlesource.com/952985
Reviewed-by: Keishi Hattori <keishi@chromium.org>
Reviewed-by: Takashi Sakamoto <tasak@google.com>
Reviewed-by: Hajime Hoshi <hajimehoshi@chromium.org>
Reviewed-by: Nick Carter <nick@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542144}
[modify] https://crrev.com/489b507f107f6faa1342b40f0fa90889fab58e05/chrome/browser/metrics/chrome_metrics_service_client.cc
[modify] https://crrev.com/489b507f107f6faa1342b40f0fa90889fab58e05/chrome/browser/metrics/chrome_metrics_service_client.h
[modify] https://crrev.com/489b507f107f6faa1342b40f0fa90889fab58e05/chrome/browser/metrics/metrics_memory_details.cc
[modify] https://crrev.com/489b507f107f6faa1342b40f0fa90889fab58e05/chrome/browser/metrics/metrics_memory_details.h
[delete] https://crrev.com/ce362d27961115aa97aba0b91c1ee728ead7898c/chrome/browser/metrics/metrics_memory_details_browsertest.cc
[modify] https://crrev.com/489b507f107f6faa1342b40f0fa90889fab58e05/chrome/browser/site_details_browsertest.cc
[modify] https://crrev.com/489b507f107f6faa1342b40f0fa90889fab58e05/chrome/test/BUILD.gn
[modify] https://crrev.com/489b507f107f6faa1342b40f0fa90889fab58e05/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9716bb2212b6d4127fb3f0fcb97ab1747499427b

commit 9716bb2212b6d4127fb3f0fcb97ab1747499427b
Author: erikchen <erikchen@chromium.org>
Date: Thu Mar 22 21:11:44 2018

Add back process count metrics used by site isolation.

Bug:  765470 
Change-Id: Id83e9d0d5d8b8a51233ec16d2bf89d55b7bb1437
Reviewed-on: https://chromium-review.googlesource.com/975665
Commit-Queue: Erik Chen <erikchen@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545248}
[modify] https://crrev.com/9716bb2212b6d4127fb3f0fcb97ab1747499427b/chrome/browser/metrics/metrics_memory_details.cc
[modify] https://crrev.com/9716bb2212b6d4127fb3f0fcb97ab1747499427b/tools/metrics/histograms/histograms.xml