Inline extensions .gypi files into GN build.

extensions/extensions_strings.gyp

Index: extensions/extensions_strings.gyp
diff --git a/extensions/extensions_strings.gyp b/extensions/extensions_strings.gyp
deleted file mode 100644
index 69f87ff2a2275a11e21e1b495e5fcefa89e1a5e8..0000000000000000000000000000000000000000
--- a/extensions/extensions_strings.gyp
+++ /dev/null
@@ -1,26 +0,0 @@
-# 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.
-
-{
-  'targets': [
-    {
-      # GN version: //extensions:strings
-      'target_name': 'extensions_strings',
-      'type': 'none',
-      'variables': {
-        'grit_out_dir': '<(SHARED_INTERMEDIATE_DIR)/extensions/strings',
-      },
-      'actions': [
-        {
-          'action_name': 'generate_extensions_strings',
-          'variables': {
-            'grit_grd_file': 'extensions_strings.grd',
-          },
-          'includes': [ '../build/grit_action.gypi' ],
-        },
-      ],
-      'includes': [ '../build/grit_target.gypi' ],
-    },
-  ],
-}