[ios] Adds support for Find in Page to the new architecture.

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",
+    "find_in_page_commands.h",
     "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" ]
 }