Move strings from webkit/ to content/.

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)',
+        ],
+      },
+    },
+  ]
+}