Add the download component and initial setup

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/chrome_build.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//printing/features/features.gni")
 import("//rlz/features/features.gni")
 import("//testing/test.gni")
@@ skipping 64 matching lines @@
     "//components/client_update_protocol:unit_tests",
     "//components/cloud_devices/common:unit_tests",
     "//components/component_updater:unit_tests",
     "//components/content_settings/core/browser:unit_tests",
     "//components/content_settings/core/common:unit_tests",
     "//components/crx_file:unit_tests",
     "//components/data_usage/core:unit_tests",
     "//components/device_event_log:unit_tests",
     "//components/dom_distiller/core:unit_tests",
     "//components/doodle:unit_tests",
+    "//components/download:unit_tests",
     "//components/favicon/core:unit_tests",
     "//components/favicon_base:unit_tests",
     "//components/flags_ui:unit_tests",
     "//components/gcm_driver:unit_tests",
     "//components/gcm_driver/crypto:unit_tests",
     "//components/google/core/browser:unit_tests",
     "//components/grpc_support/test:unit_tests",
     "//components/history/core/browser:unit_tests",
     "//components/history/core/common:unit_tests",
     "//components/image_fetcher/core:unit_tests",
@@ skipping 410 matching lines @@
       "//testing/perf",
       "//url",
     ]
 
     if (!is_ios) {
       sources += [ "discardable_memory/common/discardable_shared_memory_heap_perftest.cc" ]
       deps += [ "//components/discardable_memory/common" ]
     }
   }
 }