Extract //device/usb mocks so that they can be shared.

extensions/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("//extensions/extensions.gni")
 import("//testing/test.gni")
 import("//tools/grit/grit_rule.gni")
 import("//tools/grit/repack.gni")
 
 assert(enable_extensions)
@@ skipping 187 matching lines @@
     ":test_support",
     "shell:app_shell_lib",
 
     # TODO(yoz): find the right deps
     "//base",
     "//base:prefs_test_support",
     "//base/test:test_support",
     "//components/storage_monitor:test_support",
     "//content/test:test_support",
     "//device/bluetooth:mocks",
+    "//device/usb:mocks",
     "//mojo/environment:chromium",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/mojo/src/mojo/edk/js",
     "//third_party/mojo/src/mojo/edk/system",
     "//third_party/mojo/src/mojo/public/cpp/bindings",
   ]
 
   if (is_win) {
     deps += [ "//base/allocator" ]
   }
 
   if (is_mac) {
     deps += [ "shell:app_shell" ]  # Needed for App Shell.app's Helper.
   }
 }