Convert some GN test support targets to static libs.

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.
 
 # TODO(rockot) bug 505926: Don't include chrome files from here.
 # See chrome_browser_tests_extensions_sources below
 import("//chrome/chrome_tests.gni")
 import("//extensions/extensions.gni")
 import("//testing/test.gni")
 import("//tools/grit/grit_rule.gni")
@@ skipping 51 matching lines @@
   ]
 
   deps = [
     "//chrome/browser/media/router:mojo_bindings__generator",
     "//device/serial:serial_mojo__generator",
     "//extensions/common:mojo__generator",
     "//extensions/common/api:mojom__generator",
   ]
 }
 
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
   sources = rebase_path(extensions_gypi_values.extensions_test_support_sources,
                         ".",
                         "//extensions")
 
   # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   deps = [
     ":extensions_resources",
@@ skipping 275 matching lines @@
     "//testing/gtest",
     "//third_party/hunspell",
     "//third_party/icu",
     "//third_party/libpng",
     "//third_party/zlib",
     "//ui/base:test_support",
     "//ui/resources:ui_test_pak",
     "//ui/web_dialogs:test_support",
   ]
 }