Add precompiled headers to GN build for large targets.

ui/wm/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")
 
 component("wm") {
   sources = [
     "core/accelerator_delegate.h",
@@ skipping 52 matching lines @@
     "core/window_modality_controller.h",
     "core/window_util.cc",
     "core/window_util.h",
     "core/wm_core_switches.cc",
     "core/wm_core_switches.h",
     "core/wm_state.cc",
     "core/wm_state.h",
     "wm_export.h",
   ]
 
+  configs += [ "//build/config:precompiled_headers" ]
   defines = [ "WM_IMPLEMENTATION" ]
 
   deps = [
     "//base",
     "//skia",
     "//ui/aura",
     "//ui/base",
     "//ui/base/ime",
     "//ui/compositor",
     "//ui/events",
@@ skipping 57 matching lines @@
     "//ui/base:test_support",
     "//ui/base/ime",
     "//ui/compositor:test_support",
     "//ui/events:test_support",
     "//ui/events/platform",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
   ]
 }