[fsp] Add support for observing entries and notifying about changes.

chrome/browser/chromeos/file_system_provider/provided_file_system_interface.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/provided_file_system_interface.h"
 
 namespace chromeos {
 namespace file_system_provider {
 
 EntryMetadata::EntryMetadata() : is_directory(false), size(0) {
 }
 
 EntryMetadata::~EntryMetadata() {
 }
 
+ProvidedFileSystemInterface::ObservedEntry::ObservedEntry() : recursive(false) {
+}
+
+ProvidedFileSystemInterface::ObservedEntry::~ObservedEntry() {
+}
+
 }  // namespace file_system_provider
 }  // namespace chromeos