Fix Mac build after https://codereview.chromium.org/1407643004

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 174 matching lines @@
   INITIALIZATION_STATE_DCHECK_VALID(initialized_);
   return exception_.get();
 }
 
 std::vector<const MemoryMapRegionSnapshot*> ProcessSnapshotMac::MemoryMap()
     const {
   INITIALIZATION_STATE_DCHECK_VALID(initialized_);
   return std::vector<const MemoryMapRegionSnapshot*>();
 }
 
+std::vector<HandleSnapshot> ProcessSnapshotMac::Handles() const {
+  INITIALIZATION_STATE_DCHECK_VALID(initialized_);
+  return std::vector<HandleSnapshot>();
+}
+
 std::vector<const MemorySnapshot*> ProcessSnapshotMac::ExtraMemory() const {
   INITIALIZATION_STATE_DCHECK_VALID(initialized_);
   return std::vector<const MemorySnapshot*>();
 }
 
 void ProcessSnapshotMac::InitializeThreads() {
   const std::vector<ProcessReader::Thread>& process_reader_threads =
       process_reader_.Threads();
   for (const ProcessReader::Thread& process_reader_thread :
        process_reader_threads) {
@@ skipping 10 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