[fsp] Allow to create multiple observers for a directory, up to one per origin.

chrome/browser/chromeos/file_system_provider/observed_entry.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/chromeos/file_system_provider/observed_entry.h"
 
 namespace chromeos {
 namespace file_system_provider {
 
 ObservedEntryKey::ObservedEntryKey(const base::FilePath& entry_path,
                                    bool recursive)
     : entry_path(entry_path), recursive(recursive) {
 }
 
 ObservedEntryKey::~ObservedEntryKey() {
 }
 
 bool ObservedEntryKey::Comparator::operator()(const ObservedEntryKey& a,
                                               const ObservedEntryKey& b) const {
   if (a.entry_path != b.entry_path)
     return a.entry_path < b.entry_path;
   return a.recursive < b.recursive;
 }
 
+Subscriber::Subscriber() : persistent(false) {
+}
+
+Subscriber::~Subscriber() {
+}
+
 ObservedEntry::ObservedEntry() : recursive(false) {
 }
 
 ObservedEntry::~ObservedEntry() {
 }
 
 }  // namespace file_system_provider
 }  // namespace chromeos