PPAPI/NaCl: Reenable untrusted IPC proxy gyp flag

ppapi/ppapi_proxy_untrusted.gyp

+# Copyright (c) 2012 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.
+
+# This is the "public" ppapi.gyp file, which must have dependencies on the
+# redistributable portions of PPAPI only. This prevents circular dependencies
+# in the .gyp files (since ppapi_internal depends on parts of Chrome).
+
+{
+  'conditions': [
+    ['disable_nacl==0 and build_ppapi_ipc_proxy_untrusted==1', {
+      'includes': ['ppapi_proxy_untrusted.gypi'],
+    }],
+  ],
+  'targets': [],
+}