Add a bottom toolbar setting.

ios/clean/chrome/browser/ui/tab/BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 source_set("tab") {
   sources = [
     "tab_coordinator.h",
     "tab_coordinator.mm",
   ]
 
@@ skipping 24 matching lines @@
     "tab_container_view_controller.mm",
   ]
   deps = [
     "//ios/clean/chrome/browser/ui",
     "//ios/clean/chrome/browser/ui/animators",
     "//ios/clean/chrome/browser/ui/presenters",
   ]
   libs = [ "UIKit.framework" ]
   configs += [ "//build/config/compiler:enable_arc" ]
 }
+
+source_set("unit_tests") {
+  testonly = true
+
+  sources = [
+    "tab_coordinator_unittest.mm",
+  ]
+
+  configs += [ "//build/config/compiler:enable_arc" ]
+
+  deps = [
+    ":tab",
+    ":tab_ui",
+    "//base",
+    "//ios/chrome/browser/browser_state:test_support",
+    "//ios/shared/chrome/browser/ui/browser_list",
+    "//ios/shared/chrome/browser/ui/coordinators",
+    "//ios/shared/chrome/browser/ui/toolbar:test_support",
+    "//ios/web:test_support",
+    "//testing/gtest",
+  ]
+}