I was just thinking about this today and it looks like you are way ahead of me.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc

commit 63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc
Author: vitalybuka <vitalybuka@chromium.org>
Date: Thu Feb 23 03:44:13 2017

Remove gcdPrivate API code.

BUG= 691737 

Review-Url: https://codereview.chromium.org/2704313002
Cr-Commit-Position: refs/heads/master@{#452379}

[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/browser/extensions/BUILD.gn
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/OWNERS
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/gcd_private_api.cc
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/gcd_private_api.h
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/gcd_private_apitest.cc
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/privet_v3_context_getter.cc
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/privet_v3_context_getter.h
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/privet_v3_context_getter_unittest.cc
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/privet_v3_session.cc
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/privet_v3_session.h
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/browser/extensions/api/gcd_private/privet_v3_session_unittest.cc
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/browser/extensions/browser_context_keyed_service_factories.cc
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/browser/printing/cloud_print/privet_constants.cc
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/browser/printing/cloud_print/privet_constants.h
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/browser/printing/cloud_print/privet_http_impl.cc
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/browser/printing/cloud_print/privet_url_fetcher.cc
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/common/extensions/api/BUILD.gn
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/common/extensions/api/OWNERS
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/common/extensions/api/_api_features.json
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/common/extensions/api/_permission_features.json
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/common/extensions/api/gcd_private.idl
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/common/extensions/permissions/chrome_api_permissions.cc
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/common/extensions/permissions/permission_set_unittest.cc
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/chrome/test/BUILD.gn
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/test/data/extensions/api_test/gcd_private/api/device_info.html
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/test/data/extensions/api_test/gcd_private/api/device_info.js
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/test/data/extensions/api_test/gcd_private/api/manifest.json
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/test/data/extensions/api_test/gcd_private/api/session.html
[delete] https://crrev.com/49c68cb3932cc014111de309cba22ebe91ebc0f4/chrome/test/data/extensions/api_test/gcd_private/api/session.js
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/extensions/browser/extension_event_histogram_value.h
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/extensions/browser/extension_function_histogram_value.h
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/extensions/common/permissions/api_permission.h
[modify] https://crrev.com/63cedc505c14394c2cb47d1ec6fd3ca4b6f27bcc/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/20c4dc81ab995361bb9bc48681ff7e30a3dceb0d

commit 20c4dc81ab995361bb9bc48681ff7e30a3dceb0d
Author: thestig <thestig@chromium.org>
Date: Thu Feb 23 19:21:39 2017

Remove references to a never released Chrome app.

BUG= 691737 

CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2714643003
Cr-Commit-Position: refs/heads/master@{#452580}

[modify] https://crrev.com/20c4dc81ab995361bb9bc48681ff7e30a3dceb0d/chrome/browser/resources/feedback/js/event_handler.js
[modify] https://crrev.com/20c4dc81ab995361bb9bc48681ff7e30a3dceb0d/chrome/common/extensions/api/_permission_features.json
[modify] https://crrev.com/20c4dc81ab995361bb9bc48681ff7e30a3dceb0d/extensions/common/api/_permission_features.json