Enable ash shell and unit tests in GN build.

ui/views_content_client/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/ui.gni")
+
+component("views_content_client") {
+  testonly = true
+  sources = [
+    "views_content_browser_client.cc",
+    "views_content_browser_client.h",
+    "views_content_client.cc",
+    "views_content_client.h",
+    "views_content_client_export.h",
+    "views_content_client_main_parts.cc",
+    "views_content_client_main_parts.h",
+    "views_content_client_main_parts_chromeos.cc",
+    "views_content_client_main_parts_mac.mm",
+    "views_content_main_delegate.cc",
+  ]
+
+  defines = [ "VIEWS_CONTENT_CLIENT_IMPLEMENTATION" ]
+
+  deps = [
+    "//base",
+    "//base:i18n",
+    "//content",
+    "//content/shell:content_shell_lib",
+    "//third_party/icu",
+    "//ui/base",
+    "//ui/events",
+    "//ui/gfx",
+    "//ui/gfx/geometry",
+    "//ui/resources",
+    "//ui/resources:ui_test_pak",
+    "//ui/views",
+    "//ui/views:test_support",
+  ]
+
+  if (use_aura) {
+    sources += [
+      "views_content_client_main_parts_aura.cc",
+      "views_content_client_main_parts_aura.h",
+    ]
+
+    if (!is_chromeos) {
+      sources += [ "views_content_client_main_parts_desktop_aura.cc" ]
+    }
+
+    deps += [ "//ui/aura" ]
+  }
+}