Split feature definitions into extensions and chrome features.

tools/gritsettings/resource_ids

 # Copyright (c) 2012 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.
 #
 # This file is used to assign starting resource ids for resources and strings
 # used by Chromium.  This is done to ensure that resource ids are unique
 # across all the grd files.  If you are adding a new grd file, please add
 # a new entry to this file.
 #
 # The first entry in the file, SRCDIR, is special: It is a relative path from
@@ skipping 147 matching lines @@
   # This file is generated during the build.
   "<(SHARED_INTERMEDIATE_DIR)/content/browser/tracing/tracing_resources.grd": {
     "includes": [25750],
   },
   "ash/ash_strings.grd": {
     "messages": [26000],
   },
   "chrome/common/extensions_api_resources.grd": {
     "includes": [26500],
   },
-  # TODO(jamescook): Add extensions/extensions_resources.grd here.
+  "extensions/extensions_resources.grd": {
+    "includes": [26750],
+  },
   "extensions/extensions_strings.grd": {
     "messages": [27000],
   },
   "chrome/browser/resources/memory_internals_resources.grd": {
     "includes": [27500],
   },
   "chrome/browser/resources/password_manager_internals_resources.grd": {
     "includes": [27800],
   },
   "device/bluetooth/bluetooth_strings.grd": {
@@ skipping 18 matching lines @@
     "includes": [30250],
   },
   "components/resources/components_scaled_resources.grd": {
     "structures": [30350],
   },
   "third_party/WebKit/public/blink_resources.grd": {
     "includes": [30500],
   },
   # Resource ids starting at 31000 are reserved for projects built on Chromium.
 }