Add precompiled headers to GN build for large targets.

media/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/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/features.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//build/config/ui.gni")
 import("//media/media_options.gni")
@@ skipping 257 matching lines @@
     "video/picture.h",
     "video/video_decode_accelerator.cc",
     "video/video_decode_accelerator.h",
     "video/video_encode_accelerator.cc",
     "video/video_encode_accelerator.h",
   ]
 
   configs += [
     ":media_config",
     ":media_implementation",
+    "//build/config:precompiled_headers",
 
     # TODO(wolenetz): Fix size_t to int trunctaion in win64.
     # See http://crbug.com/171009
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
   all_dependent_configs = [ ":media_dependent_config" ]
 
   allow_circular_includes_from = []
   cflags = []
   libs = []
@@ skipping 486 matching lines @@
       "//media/base:test_support",
       "//media/test:pipeline_integration_tests",
       "//testing/gmock",
       "//testing/gtest",
       "//third_party/ffmpeg",
       "//ui/gfx/geometry",
       "//ui/gfx:test_support",
     ]
   }
 }