Create a about handler component.

components/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//tools/grit/repack.gni")
 
 # Collection of all components. You wouldn't link to this, but this is rather
 # to reference the files so they can be compiled by the build system.
 group("all_components") {
   testonly = true  # You shouldn't actually link to this.
   visibility = [ "//:*" ]  # Only for the root targets to bring in.
 
   deps = [
+    "//components/about_handler",
     "//components/auto_login_parser",
     "//components/autofill/content/browser",
     "//components/autofill/content/common",
     "//components/autofill/content/renderer",
     "//components/bookmarks/browser",
     "//components/bookmarks/common",
     "//components/bookmarks/managed",
     "//components/bookmarks/test",
     "//components/captive_portal",
     "//components/cdm/browser",
@@ skipping 475 matching lines @@
 
   deps = [
     "//base",
     "//base/test:test_support_perf",
     "//testing/gtest",
     "//testing/perf",
     "//content/test:test_support",
     "//components/visitedlink/browser",
   ]
 }