Add precompiled headers to GN build for large targets.

media/base/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/ui.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//media/media_options.gni")
@@ skipping 193 matching lines @@
   defines = []
   public_deps = []
   deps = [
     "//ui/events:events_base",
     "//skia",
   ]
   libs = []
   configs += [
     # This target uses the ALLOCATOR_SHIM define.
     "//base/allocator:allocator_shim_define",
+    "//build/config:precompiled_headers",
     "//media:media_config",
     "//media:media_implementation",
   ]
 
   if (media_use_ffmpeg) {
     sources += [
       "audio_video_metadata_extractor.cc",
       "audio_video_metadata_extractor.h",
       "container_names.cc",
       "container_names.h",
@@ skipping 297 matching lines @@
       if (is_posix) {
         yasm_flags += [ "-DELF" ]
         if (current_cpu == "x64") {
           # TODO(ajwong): Why isn't this true in mac?
           yasm_flags += [ "-DPIC" ]
         }
       }
     }
   }
 }