Add precompiled headers to GN build for large targets.

components/policy/core/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/features.gni")
 
 source_set("common") {
   visibility = [ "//components/policy/*" ]
 
   defines = [ "POLICY_COMPONENT_IMPLEMENTATION" ]
@@ skipping 111 matching lines @@
       "schema.h",
       "schema_internal.h",
       "schema_map.cc",
       "schema_map.h",
       "schema_registry.cc",
       "schema_registry.h",
       "schema_registry_tracking_policy_provider.cc",
       "schema_registry_tracking_policy_provider.h",
     ]
 
+    configs += [ "//build/config:precompiled_headers" ]
+
     deps = [
       "//base:prefs",
       "//base/third_party/dynamic_annotations",
       "//components/json_schema",
       "//components/policy",
       "//components/policy/proto",
       "//google_apis",
       "//net",
       "//third_party/re2",
       "//url",
@@ skipping 59 matching lines @@
       "policy_service.cc",
       "policy_service.h",
       "policy_service_stub.cc",
       "policy_service_stub.h",
     ]
     deps = [
       "//base",
     ]
   }
 }