Get rid of app/ directory as it's no longer used (finally).

app/app_base.gypi

-# Copyright (c) 2011 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.
-
-{
-  'variables': {
-    'chromium_code': 1,
-  },
-  'targets': [
-    {
-      'target_name': 'app_base',
-      'type': 'static_library',
-      'dependencies': [
-        '../base/base.gyp:base',
-        '../third_party/sqlite/sqlite.gyp:sqlite',
-      ],
-      'sources': [
-        '../sql/connection.cc',
-        '../sql/connection.h',
-        '../sql/diagnostic_error_delegate.h',
-        '../sql/init_status.h',
-        '../sql/meta_table.cc',
-        '../sql/meta_table.h',
-        '../sql/statement.cc',
-        '../sql/statement.h',
-        '../sql/transaction.cc',
-        '../sql/transaction.h',
-      ],
-    },
-  ],
-}