As proof that the code is not used, https://chromium-review.googlesource.com/c/chromium/src/+/722358 just remove the dependency on the //ios/chrome/browser/ui/contextual_search dependency and all targets build and all tests pass.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2bd5f03512bcb0b0632366109612ea4e9c4b7ce2

commit 2bd5f03512bcb0b0632366109612ea4e9c4b7ce2
Author: Sylvain Defresne <sdefresne@chromium.org>
Date: Tue Oct 17 09:28:02 2017

Stop compiling ios/chrome/browser/ui/contextual_search.

Code is compiled but never used, so as a first step before
deleting the code, stop compiling it (this proves that it
is really unused).

Bug:  775332 
Change-Id: Ie38fba7c8f27bf10301c0e37187d1ee69df0ca86
Reviewed-on: https://chromium-review.googlesource.com/722358
Commit-Queue: Mark Cogan <marq@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509334}
[modify] https://crrev.com/2bd5f03512bcb0b0632366109612ea4e9c4b7ce2/ios/chrome/app/BUILD.gn
[modify] https://crrev.com/2bd5f03512bcb0b0632366109612ea4e9c4b7ce2/ios/chrome/browser/ui/BUILD.gn
[modify] https://crrev.com/2bd5f03512bcb0b0632366109612ea4e9c4b7ce2/ios/chrome/test/BUILD.gn

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/chrome/ios_internal.git/+/74a2142daa0678a0574bc06c4f84f9ae7606c482

commit 74a2142daa0678a0574bc06c4f84f9ae7606c482
Author: Sylvain Defresne <sdefresne@google.com>
Date: Thu Oct 19 15:40:29 2017

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0

commit b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0
Author: Sylvain Defresne <sdefresne@chromium.org>
Date: Thu Oct 19 16:02:47 2017

Remove dead code from ContextualSearch.

Inspecting the code revealed that ContextualSearchController -panel
property was never set, and that the delegate passed to initializer
was always a mock with no method mocked.

It follows that _panelView, _searchResultView and _headerView are
always nil, and the delegate method always returned default value
and were doing nothing. Remove all code that can be proved to be
dead based on those observation and the fact that calling a method
on nil received does nothing and return the default value for the
method selector.

Bug:  775332 
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I9fbd18c97e1f19f91384bb54d3102e2509f4ccb0
Reviewed-on: https://chromium-review.googlesource.com/727472
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510099}
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/app/strings/ios_strings.grd
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/app/theme/default_100_percent/contextual_search_header.png
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/app/theme/default_200_percent/contextual_search_header.png
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/app/theme/default_300_percent/contextual_search_header.png
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/app/theme/ios_theme_resources.grd
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/browser/providers/images/chromium_branded_image_provider.h
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/browser/providers/images/chromium_branded_image_provider.mm
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/browser/ui/contextual_search/BUILD.gn
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/browser/ui/contextual_search/contextual_search_controller.h
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/browser/ui/contextual_search/contextual_search_controller.mm
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_header_view.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_header_view.mm
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/browser/ui/contextual_search/contextual_search_js_unittest.mm
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_mask_view.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_mask_view.mm
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/browser/ui/contextual_search/contextual_search_metrics.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_panel_protocols.h
[add] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/chrome/browser/ui/contextual_search/contextual_search_panel_state.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_panel_view.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_panel_view.mm
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_promo_view.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_promo_view.mm
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_results_view.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_results_view.mm
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_wrangler.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/contextual_search_wrangler.mm
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/panel_configuration.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/panel_configuration.mm
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/resources/BUILD.gn
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/resources/expand_less.imageset/Contents.json
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/resources/expand_less.imageset/expand_less.png
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/resources/expand_less.imageset/expand_less@2x.png
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/resources/expand_less.imageset/expand_less@3x.png
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/settings/BUILD.gn
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/settings/contextual_search_collection_view_controller.h
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/settings/contextual_search_collection_view_controller.mm
[delete] https://crrev.com/6f4d6990290d7a93807ea92e1112fceb5cb4dda6/ios/chrome/browser/ui/contextual_search/settings/contextual_search_collection_view_controller_unittest.mm
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/public/provider/chrome/browser/images/branded_image_provider.h
[modify] https://crrev.com/b9b5af0f4a1bfb870f7a97dd0afd337ca8a591d0/ios/public/provider/chrome/browser/images/branded_image_provider.mm

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

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

Is it time to remove Touch To Search now?

Yep. 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a75503e9accc2c3e0dd8f8b9ed08b6d1318b29eb

commit a75503e9accc2c3e0dd8f8b9ed08b6d1318b29eb
Author: Mark Cogan <marq@google.com>
Date: Tue Oct 23 12:28:06 2018

[iOS] Remove contextual search implementation.

This has been moribund for several years.

Bug:  775332 
Change-Id: Ie27ae997ebc9ba7c8d0794e6c51375b5caa71b39
Reviewed-on: https://chromium-review.googlesource.com/c/1296171
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601913}
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/BUILD.gn
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/OWNERS
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/README.md
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_context.cc
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_context.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_controller.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_controller.mm
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_delegate.cc
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_delegate.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_highlighter_view.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_highlighter_view.mm
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_js_unittest.mm
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_metrics.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_metrics.mm
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/contextual_search_panel_state.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/js_contextual_search_manager.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/js_contextual_search_manager.mm
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/protos/BUILD.gn
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/protos/client_discourse_context.proto
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/resources/contextualsearch.js
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/resources/contextualsearch_unittest.js
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/switches.cc
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/switches.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/touch_to_search_permissions_mediator+testing.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/touch_to_search_permissions_mediator+testing.mm
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/touch_to_search_permissions_mediator.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/touch_to_search_permissions_mediator.mm
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/touch_to_search_permissions_mediator_unittest.mm
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/window_gesture_observer.h
[delete] https://crrev.com/8ce5c1c2133767847ce7ebcef0853dbdeca326dc/ios/chrome/browser/ui/contextual_search/window_gesture_observer.mm
[modify] https://crrev.com/a75503e9accc2c3e0dd8f8b9ed08b6d1318b29eb/ios/chrome/test/BUILD.gn

 Issue 884677  has been merged into this issue.