Add precompiled headers to GN build for large targets.

remoting/protocol/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("//remoting/remoting_srcs.gni")
 
 source_set("protocol") {
   sources = rebase_path(remoting_srcs_gypi_values.remoting_protocol_sources,
                         ".",
                         "//remoting")
 
   configs += [
+    "//build/config:precompiled_headers",
     "//build/config/compiler:no_size_t_to_int_warning",
     "//build/config/compiler:wexit_time_destructors",
   ]
 
   public_deps = [
     "//remoting/proto",
     "//third_party/libjingle",
   ]
   deps = [
     "//base",
@@ skipping 63 matching lines @@
     "third_party_authenticator_unittest.cc",
     "v2_authenticator_unittest.cc",
   ]
 
   deps = [
     ":test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }