Add RandomString() and its test, and use it everywhere it makes sense

util/util_test.gyp

 # Copyright 2014 The Crashpad Authors. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 41 matching lines @@
         'mach/mach_message_server_test.cc',
         'mach/mach_message_test.cc',
         'mach/notify_server_test.cc',
         'mach/scoped_task_suspend_test.cc',
         'mach/symbolic_constants_mach_test.cc',
         'mach/task_memory_test.cc',
         'misc/clock_test.cc',
         'misc/initialization_state_dcheck_test.cc',
         'misc/initialization_state_test.cc',
         'misc/scoped_forbid_return_test.cc',
+        'misc/random_string_test.cc',
         'misc/uuid_test.cc',
         'net/http_body_test.cc',
         'net/http_body_test_util.cc',
         'net/http_body_test_util.h',
         'net/http_multipart_builder_test.cc',
         'net/http_transport_test.cc',
         'numeric/checked_address_range_test.cc',
         'numeric/checked_range_test.cc',
         'numeric/in_range_cast_test.cc',
         'numeric/int128_test.cc',
@@ skipping 58 matching lines @@
               ],
               'RandomizedBaseAddress': '1',  # /DYNAMICBASE:NO.
               'FixedBaseAddress': '2',  # /FIXED.
             },
           },
         },
       ]
     }],
   ],
 }