chrome: Add out-of-line copy ctors for complex classes.

chrome/browser/sync_file_system/drive_backend/tracker_id_set.cc

 // Copyright 2014 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.
 
 #include "chrome/browser/sync_file_system/drive_backend/tracker_id_set.h"
 
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "chrome/browser/sync_file_system/drive_backend/metadata_database.pb.h"
 
 namespace sync_file_system {
 namespace drive_backend {
 
 TrackerIDSet::TrackerIDSet() : active_tracker_(0) {}
 
+TrackerIDSet::TrackerIDSet(const TrackerIDSet& other) = default;
+
 TrackerIDSet::~TrackerIDSet() {}
 
 void TrackerIDSet::Insert(const FileTracker& tracker) {
   if (tracker.active())
     InsertActiveTracker(tracker.tracker_id());
   else
     InsertInactiveTracker(tracker.tracker_id());
 }
 
 void TrackerIDSet::InsertActiveTracker(int64_t tracker_id) {
@@ skipping 26 matching lines @@
 }
 
 void TrackerIDSet::Deactivate(int64_t tracker_id) {
   DCHECK_EQ(active_tracker_, tracker_id);
   DCHECK(ContainsKey(tracker_ids_, tracker_id));
   active_tracker_ = 0;
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system