Convert some GN test support targets to static libs.

remoting/signaling/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.
 
 import("//remoting/remoting_srcs.gni")
 
-source_set("signaling") {
+static_library("signaling") {
   sources = rebase_path(remoting_srcs_gypi_values.remoting_signaling_sources,
                         ".",
                         "//remoting")
 
   configs += [
     "//build/config/compiler:no_size_t_to_int_warning",
     "//build/config/compiler:wexit_time_destructors",
   ]
 
   public_deps = [
@@ skipping 11 matching lines @@
 
   if (is_nacl) {
     sources -= [
       "log_to_server.cc",
       "server_log_entry.cc",
       "xmpp_signal_strategy.cc",
     ]
   }
 }
 
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
 
   sources = [
     "fake_signal_strategy.cc",
     "fake_signal_strategy.h",
     "mock_signal_strategy.cc",
     "mock_signal_strategy.h",
   ]
 
   public_deps = [
@@ skipping 16 matching lines @@
     "xmpp_signal_strategy_unittest.cc",
     "xmpp_stream_parser_unittest.cc",
   ]
 
   deps = [
     ":test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }