[mojo] Delete third_party/mojo

mojo/mojo_public_system_unittests.isolate

 # Copyright 2015 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.
 {
   'includes': [
     '../../base/base.isolate',
   ],
   'conditions': [
     ['OS=="win" or OS=="mac" or OS=="linux"', {
       'variables': {
@@ skipping 24 matching lines @@
     }],
     ['OS=="mac"', {
       'variables': {
         'files': [
           '<(PRODUCT_DIR)/libmojo_public_test_support.dylib',
         ],
       },
     }],
   ],
 }