Add precompiled headers to GN build for large targets.

content/test/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("//build/config/chrome_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/module_args/v8.gni")
 import("//testing/test.gni")
 import("//third_party/mojo/src/mojo/public/tools/bindings/mojom.gni")
 
 content_tests_gypi_values =
     exec_script("//build/gypi_to_gn.py",
                 [
                   rebase_path("../content_tests.gypi"),
                   "--replace=<(SHARED_INTERMEDIATE_DIR)=$root_gen_dir",
                 ],
                 "scope",
                 [ "../content_tests.gypi" ])
 
 # GYP version //content/content_tests.gypi:test_support_content
 source_set("test_support") {
   testonly = true
+  configs += [ "//build/config:precompiled_headers" ]
   public_deps = [
     "//content/public/app:both",
     "//content/public/browser",
     "//content/public/common",
   ]
   deps = [
     "//cc/blink",
     "//net:test_support",
     "//skia",
     "//storage/common",
@@ skipping 226 matching lines @@
 # TODO(GYP) enable content_browsertests on Mac when it links.
 if (!is_mac) {
   test("content_browsertests") {
     sources =
         rebase_path(content_tests_gypi_values.content_browsertests_sources,
                     ".",
                     "//content")
 
     defines = [ "HAS_OUT_OF_PROC_TEST_RUNNER" ]
 
-    configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
+    configs += [
+      "//build/config:precompiled_headers",
+      "//build/config/compiler:no_size_t_to_int_warning",
+    ]
 
     deps = [
       ":browsertest_support",
       ":web_ui_test_mojo_bindings",
       "//base/allocator",
       "//base/test:test_support",
       "//content/common:mojo_bindings",
       "//content/gpu",
       "//content/public/common",
       "//content/public/plugin",
@@ skipping 138 matching lines @@
       sources -=
           [ "../browser/web_contents/web_contents_view_aura_browsertest.cc" ]
     }
   }
 }
 
 test("content_unittests") {
   sources = rebase_path(content_tests_gypi_values.content_unittests_sources,
                         ".",
                         "//content")
+
+  configs += [ "//build/config:precompiled_headers" ]
+
   deps = [
     ":test_support",
     "//base/allocator",
     "//base/test:test_support",
     "//content/browser/background_sync:background_sync_proto",
     "//content/browser/notifications:notification_proto",
     "//content/browser/service_worker:service_worker_proto",
     "//content/browser/speech/proto",
     "//content/common:mojo_bindings",
     "//content/public/browser",
@@ skipping 260 matching lines @@
       "//testing/gtest",
       "//third_party/WebKit/public:blink",
       "//ui/base",
       "//ui/gfx",
       "//ui/gfx/geometry",
       "//ui/gl",
       "//ui/gl:test_support",
     ]
   }
 }