Additionally, record additions and removal of printers by protocol.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d86afbe21be3199f9a0674b2d68ac58d1e1737c6

commit d86afbe21be3199f9a0674b2d68ac58d1e1737c6
Author: skau <skau@chromium.org>
Date: Fri May 26 01:04:01 2017

Track printer protocol usage for CUPS printers.

Add a metric called CUPS.PrinterProtocol that records the protocol for
a selected printer. This will be used to track usage of the various
protocols to prioritize effort.

BUG= 726103 

Review-Url: https://codereview.chromium.org/2903113002
Cr-Commit-Position: refs/heads/master@{#474859}

[modify] https://crrev.com/d86afbe21be3199f9a0674b2d68ac58d1e1737c6/chrome/browser/ui/webui/print_preview/printer_backend_proxy_chromeos.cc
[modify] https://crrev.com/d86afbe21be3199f9a0674b2d68ac58d1e1737c6/chromeos/printing/printer_configuration.cc
[modify] https://crrev.com/d86afbe21be3199f9a0674b2d68ac58d1e1737c6/chromeos/printing/printer_configuration.h
[modify] https://crrev.com/d86afbe21be3199f9a0674b2d68ac58d1e1737c6/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/d86afbe21be3199f9a0674b2d68ac58d1e1737c6/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6d46ea6e7636ecdb53b00795f4893cbc32694f30

commit 6d46ea6e7636ecdb53b00795f4893cbc32694f30
Author: skau <skau@chromium.org>
Date: Thu Jun 01 01:59:36 2017

Log printer additions and removals by protocol.

In order to track printer churn, we record an event when a printer is
succesfully added and when a printer is removed in the settings dialogs.
This data is tracked by protocol.

BUG= 726103 

Review-Url: https://codereview.chromium.org/2903883003
Cr-Commit-Position: refs/heads/master@{#476146}

[modify] https://crrev.com/6d46ea6e7636ecdb53b00795f4893cbc32694f30/chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.cc
[modify] https://crrev.com/6d46ea6e7636ecdb53b00795f4893cbc32694f30/tools/metrics/histograms/histograms.xml

Request merge to M60.  Logging verified on Canary 61.0.3119.0 using a Kip.

Your change meets the bar and is auto-approved for M60. Please go ahead and merge the CL to branch 3112 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), josafat@(ChromeOS), bustamante@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/11389fcea63dd43c32a78a9cc2342e82cdff598c

commit 11389fcea63dd43c32a78a9cc2342e82cdff598c
Author: Sean Kau <skau@chromium.org>
Date: Tue Jun 06 21:18:22 2017

Log printer additions and removals by protocol.

In order to track printer churn, we record an event when a printer is
succesfully added and when a printer is removed in the settings dialogs.
This data is tracked by protocol.

BUG= 726103 

Review-Url: https://codereview.chromium.org/2903883003
Cr-Original-Commit-Position: refs/heads/master@{#476146}
Review-Url: https://codereview.chromium.org/2923893002 .
Cr-Commit-Position: refs/branch-heads/3112@{#210}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}

[modify] https://crrev.com/11389fcea63dd43c32a78a9cc2342e82cdff598c/chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.cc
[modify] https://crrev.com/11389fcea63dd43c32a78a9cc2342e82cdff598c/tools/metrics/histograms/histograms.xml