Allow generation of a chromium outdirs when enable_extensions=false

extensions/browser/api/web_request/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.
 
+import("//extensions/features/features.gni")
+
+assert(enable_extensions,
+       "Cannot depend on extensions because enable_extensions=false.")
+
 source_set("web_request") {
   sources = [
     "form_data_parser.cc",
     "form_data_parser.h",
     "upload_data_presenter.cc",
     "upload_data_presenter.h",
     "web_request_api.cc",
     "web_request_api.h",
     "web_request_api_constants.cc",
     "web_request_api_constants.h",
@@ skipping 21 matching lines @@
     "//content/public/common",
     "//extensions/common/api",
     "//extensions/strings",
     "//third_party/re2",
   ]
 
   public_deps = [
     "//extensions/browser:browser_sources",
   ]
 }