Add precompiled headers to GN build for large targets.

ui/gfx/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/ui.gni")
 import("//testing/test.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
@@ skipping 214 matching lines @@
     "win/metro_mode.h",
     "win/scoped_set_map_mode.h",
     "win/singleton_hwnd.cc",
     "win/singleton_hwnd.h",
     "win/singleton_hwnd_observer.cc",
     "win/singleton_hwnd_observer.h",
     "win/window_impl.cc",
     "win/window_impl.h",
   ]
 
-  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-  configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
+  configs += [
+    "//build/config:precompiled_headers",
+
+    # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+    "//build/config/compiler:no_size_t_to_int_warning",
+  ]
 
   defines = [ "GFX_IMPLEMENTATION" ]
 
   deps = [
     ":gfx_export",
     "//base",
     "//base:i18n",
     "//base:base_static",
     "//base/third_party/dynamic_annotations",
     "//skia",
@@ skipping 345 matching lines @@
 if (is_android) {
   generate_jni("gfx_jni_headers") {
     sources = [
       "../android/java/src/org/chromium/ui/gfx/BitmapHelper.java",
       "../android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java",
       "../android/java/src/org/chromium/ui/gfx/ViewConfigurationHelper.java",
     ]
     jni_package = "gfx"
   }
 }