Encode all grit outputs in .gn files

extensions/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("//tools/grit/grit_rule.gni")
 
 # GYP version: extensions/extensions_resources.gyp:extensions_resources
 group("extensions_resources") {
   deps = [
     ":extensions_renderer_resources",
     ":extensions_resources_grd",
   ]
 }
 
 # GYP version: extensions/extensions_resources.gyp:extensions_resources
 #              (exntensions_resources action)
 grit("extensions_resources_grd") {
   source = "extensions_resources.grd"
+  outputs = [
+    "grit/extensions_resources.h",
+    "extensions_resources.pak",
+  ]
 }
 
 # GYP version: extensions/extensions_resources.gyp:extensions_resources
 #              (exntensions_renderer_resources action)
 grit("extensions_renderer_resources") {
   source = "renderer/resources/extensions_renderer_resources.grd"
+  outputs = [
+    "grit/extensions_renderer_resources.h",
+    "extensions_renderer_resources.pak",
+  ]
 }