Inline content_[tests/browser/android].gypi into GN build.

content/app/strings/content_strings.gyp

-# 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: //content/app/strings
-      'target_name': 'content_strings',
-      'type': 'none',
-      'variables': {
-        'grit_out_dir': '<(SHARED_INTERMEDIATE_DIR)/content/app/strings',
-      },
-      'actions': [
-        {
-          'action_name': 'generate_content_strings',
-          'variables': {
-            'grit_grd_file': 'content_strings.grd',
-          },
-          'includes': [ '../../../build/grit_action.gypi' ],
-        },
-      ],
-      'direct_dependent_settings': {
-        'include_dirs': [
-          '<(SHARED_INTERMEDIATE_DIR)',
-        ],
-      },
-    },
-  ]
-}