Add ConstThreadState to mach_extensions.h and use it everywhere

snapshot/mac/process_snapshot_mac.cc

 // 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 44 matching lines @@
   INITIALIZATION_STATE_SET_VALID(initialized_);
   return true;
 }
 
 bool ProcessSnapshotMac::InitializeException(
     thread_t exception_thread,
     exception_type_t exception,
     const mach_exception_data_type_t* code,
     mach_msg_type_number_t code_count,
     thread_state_flavor_t flavor,
-    const natural_t* state,
+    ConstThreadState state,
     mach_msg_type_number_t state_count) {
   INITIALIZATION_STATE_DCHECK_VALID(initialized_);
   DCHECK(!exception_);
 
   exception_.reset(new internal::ExceptionSnapshotMac());
   if (!exception_->Initialize(&process_reader_,
                               exception_thread,
                               exception,
                               code,
                               code_count,
@@ skipping 125 matching lines @@
   for (const ProcessReader::Module& process_reader_module :
        process_reader_modules) {
     auto module = make_scoped_ptr(new internal::ModuleSnapshotMac());
     if (module->Initialize(&process_reader_, process_reader_module)) {
       modules_.push_back(module.release());
     }
   }
 }
 
 }  // namespace crashpad