[ios] Adds a CommandDispatcher to Browser.

ios/clean/chrome/browser/ui/commands/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("commands") {
   sources = [
-    "command_dispatcher.h",
-    "command_dispatcher.mm",
     "settings_commands.h",
     "tab_commands.h",
     "tab_grid_commands.h",
     "toolbar_commands.h",
   ]
   deps = [
     "//base",
   ]
 
   configs += [ "//build/config/compiler:enable_arc" ]
 }
-
-source_set("unit_tests") {
-  testonly = true
-  sources = [
-    "command_dispatcher_unittest.mm",
-  ]
-  deps = [
-    ":commands",
-    "//base",
-    "//testing/gtest",
-  ]
-
-  configs += [ "//build/config/compiler:enable_arc" ]
-}