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}

ios/chrome/app/BUILD.gn

@@ -185,7 +185,6 @@ source_set("app_internal") {
     "//ios/chrome/browser/ui:ui_internal",
     "//ios/chrome/browser/ui/authentication",
     "//ios/chrome/browser/ui/commands",
-    "//ios/chrome/browser/ui/contextual_search",
     "//ios/chrome/browser/ui/downloads",
     "//ios/chrome/browser/ui/first_run",
     "//ios/chrome/browser/ui/history",

ios/chrome/browser/ui/BUILD.gn

@@ -304,7 +304,6 @@ source_set("ui_internal") {
     "//ios/chrome/browser/ui/commands",
     "//ios/chrome/browser/ui/content_suggestions:content_suggestions_constant",
     "//ios/chrome/browser/ui/context_menu",
-    "//ios/chrome/browser/ui/contextual_search",
     "//ios/chrome/browser/ui/dialogs:dialogs_internal",
     "//ios/chrome/browser/ui/elements:elements_internal",
     "//ios/chrome/browser/ui/find_bar",

ios/chrome/test/BUILD.gn

@@ -179,8 +179,6 @@ test("ios_chrome_unittests") {
     "//ios/chrome/browser/ui/content_suggestions/cells:unit_tests",
     "//ios/chrome/browser/ui/content_suggestions/identifier:unit_tests",
     "//ios/chrome/browser/ui/context_menu:unit_tests",
-    "//ios/chrome/browser/ui/contextual_search:unit_tests",
-    "//ios/chrome/browser/ui/contextual_search/settings:unit_tests",
     "//ios/chrome/browser/ui/coordinators:unit_tests",
     "//ios/chrome/browser/ui/dialogs:unit_tests",
     "//ios/chrome/browser/ui/dialogs:unit_tests_internal",