Annotate large GN targets for precompiled headers

ppapi/proxy/BUILD.gn

 # Copyright 2015 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.
 
 config("proxy_implementation") {
   defines = [ "PPAPI_PROXY_IMPLEMENTATION" ]
 }
 
 component("proxy") {
   output_name = "ppapi_proxy"
@@ skipping 247 matching lines @@
       "ppp_content_decryptor_private_proxy.h",
       "ppp_instance_private_proxy.cc",
       "ppp_instance_private_proxy.h",
       "ppp_video_decoder_proxy.cc",
       "ppp_video_decoder_proxy.h",
       "video_capture_resource.cc",
       "video_capture_resource.h",
     ]
   }
 
-  configs += [ ":proxy_implementation" ]
+  configs += [
+    ":proxy_implementation",
+    "//build/config:precompiled_headers",
+  ]
 
   deps = [
     "//base",
     "//gpu/command_buffer/client:gles2_implementation",
     "//gpu/ipc",
     "//ipc",
     "//media:shared_memory_support",
     "//ppapi/c",
     "//ppapi/proxy:ipc_sources",
     "//ppapi/shared_impl",
@@ skipping 81 matching lines @@
   deps = [
     "//base/test:test_support",
     "//ipc",
     "//ipc:test_support",
     "//ppapi/proxy",
     "//ppapi/shared_impl",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }