Revert of Use Mojo pipes to signal sync IPC events

ipc/ipc.gypi

 # 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.
 
 {
   'target_defaults': {
     'variables': {
       'ipc_target': 0,
     },
     'target_conditions': [
@@ skipping 80 matching lines @@
           'mach_port_attachment_mac.cc',
           'mach_port_attachment_mac.h',
           'mach_port_mac.cc',
           'mach_port_mac.h',
           'message_filter.cc',
           'message_filter.h',
           'message_filter_router.cc',
           'message_filter_router.h',
           'message_router.cc',
           'message_router.h',
-          'mojo_event.cc',
-          'mojo_event.h',
           'param_traits_log_macros.h',
           'param_traits_macros.h',
           'param_traits_read_macros.h',
           'param_traits_write_macros.h',
           'placeholder_brokerable_attachment.cc',
           'placeholder_brokerable_attachment.h',
           'struct_constructor_macros.h',
           'struct_destructor_macros.h',
           'unix_domain_socket_util.cc',
           'unix_domain_socket_util.h',
@@ skipping 15 matching lines @@
           ['OS == "win" or OS == "ios"', {
             'sources!': [
               'unix_domain_socket_util.cc',
             ],
           }],
         ],
       }],
     ],
   },
 }