Add precompiled headers to GN build for large targets.

extensions/common/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/crypto.gni")
 import("//build/config/features.gni")
 import("//extensions/extensions.gni")
 import("//third_party/mojo/src/mojo/public/tools/bindings/mojom.gni")
 
 # GYP version: extensions/extensions.gyp:extensions_common_constants
@@ skipping 16 matching lines @@
 
   # GYP version: extensions/extensions.gyp:extensions_common
   # This must be a static library because extensions common depends on
   # GetTrustedICAPublicKey in extensions/browser which isn't always linked
   # in. TODO(brettw): This reverse dependency should be fixed.
   static_library("common") {
     sources = rebase_path(extensions_gypi_values.extensions_common_sources,
                           ".",
                           "//extensions")
 
-    # 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",
+    ]
 
     deps = [
       ":common_constants",
       ":mojo",
 
       # TODO(benwells): figure out what to do with the api target and
       # api resources compiled into the chrome resource bundle.
       # http://crbug.com/162530
       "//chrome:resources",
       "//components/crx_file",
@@ skipping 31 matching lines @@
 
     if (enable_nacl) {
       nacl_sources =
           rebase_path(extensions_gypi_values.extensions_common_sources_nacl,
                       ".",
                       "//extensions")
       sources += nacl_sources
     }
   }
 }  # enable_extensions