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

chrome/test/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/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/module_args/v8.gni")
 import("//testing/test.gni")
@@ skipping 1300 matching lines @@
       ]
     }
 
     if (enable_extensions) {
       sources +=
           rebase_path(unit_gypi_values.chrome_unit_tests_extensions_sources,
                       ".",
                       "//chrome")
       deps += [
         "//chrome/common/extensions/api",
+        "//device/usb:mocks",
         "//extensions:extensions_resources",
         "//extensions/strings",
       ]
       if (enable_configuration_policy) {
         sources += rebase_path(
                 unit_gypi_values.chrome_unit_tests_extensions_policy_sources,
                 ".",
                 "//chrome")
       }
       if (!is_chromeos) {
@@ skipping 429 matching lines @@
       }
 
       if (cld_version == 0 || cld_version == 2) {
         # Use whatever CLD2 data access mode that the
         # application embedder is using.
         deps += [ "//third_party/cld_2:cld2_platform_impl" ]
       }
     }
   }
 }