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

app/app.gyp

-# 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,
-  },
-  'includes': [
-    'app_base.gypi',
-  ],
-  'targets': [
-    {
-      'target_name': 'app_unittests',
-      'type': 'executable',
-      'dependencies': [
-        'app_base',
-        '../base/base.gyp:test_support_base',
-        '../testing/gtest.gyp:gtest',
-      ],
-      'sources': [
-        '../sql/run_all_unittests.cc',
-        '../sql/connection_unittest.cc',
-        '../sql/sqlite_features_unittest.cc',
-        '../sql/statement_unittest.cc',
-        '../sql/transaction_unittest.cc',
-      ],
-      'include_dirs': [
-        '..',
-      ],
-      'conditions': [
-        ['os_posix==1 and OS!="mac"', {
-          'conditions': [
-            ['linux_use_tcmalloc==1', {
-              'dependencies': [
-                '../base/allocator/allocator.gyp:allocator',
-              ],
-            }],
-          ],
-        }],
-      ],
-    },
-  ],
-}