Fix build dependencies in src/extensions

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("//tools/grit/grit_rule.gni")
 
 # GYP version: extensions/extensions_resources.gyp:extensions_resources
 group("extensions_resources") {
   deps = [
     ":extensions_renderer_resources",
@@ skipping 24 matching lines @@
     "//device/serial:serial_mojo",
   ]
 }
 
 source_set("test_support") {
   sources = [
     "browser/api/dns/mock_host_resolver_creator.cc",
     "browser/api/dns/mock_host_resolver_creator.h",
     "browser/api_test_utils.cc",
     "browser/api_test_utils.h",
+    "browser/extensions_test.cc",
+    "browser/extensions_test.h",
     "browser/test_extensions_browser_client.cc",
     "browser/test_extensions_browser_client.h",
     "browser/test_management_policy.cc",
     "browser/test_management_policy.h",
     "browser/test_runtime_api_delegate.cc",
     "browser/test_runtime_api_delegate.h",
     "common/extension_builder.cc",
     "common/extension_builder.h",
     "common/test_util.cc",
     "common/test_util.h",
@@ skipping 11 matching lines @@
     "//net:test_support",
     "//testing/gtest",
   ]
 
   if (is_win) {
     cflags = [
       "/wd4267", # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     ]
   }
 }