Get 'gn_all' building on iOS

components/webp_transcode/BUILD.gn

 # Copyright 2015 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.
 
 source_set("webp_transcode") {
   sources = [
     "webp_decoder.h",
     "webp_decoder.mm",
     "webp_network_client.h",
     "webp_network_client.mm",
@@ skipping 13 matching lines @@
   testonly = true
   sources = [
     "webp_decoder_unittest.mm",
     "webp_network_client_unittest.mm",
   ]
 
   deps = [
     ":webp_transcode",
     "//base",
     "//net",
+    "//net:test_support",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/ocmock",
   ]
 }