Fix a bug that unmounting devices on the policy update can be a busy loop.

chrome/browser/chromeos/file_manager/fake_disk_mount_manager.cc

 // Copyright 2013 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_manager/fake_disk_mount_manager.h"
 
 #include "base/callback.h"
 
 namespace file_manager {
 
@@ skipping 87 matching lines @@
 
   MountPointMap::iterator iter = mount_points_.find(mount_path);
   if (iter == mount_points_.end())
     return;
   const MountPointInfo mount_point = iter->second;
   mount_points_.erase(iter);
   FOR_EACH_OBSERVER(DiskMountManager::Observer, observers_,
                     OnMountEvent(DiskMountManager::UNMOUNTING,
                                  chromeos::MOUNT_ERROR_NONE,
                                  mount_point));
-  // Currently |callback| is just ignored.
+  // Enqueue callback so that |FakeDiskMountManager::FinishAllUnmountRequest()|
+  // can call them.
+  pending_unmount_callbacks_.push(callback);
+}
+
+bool FakeDiskMountManager::FinishAllUnmountPathRequests() {
+  if (pending_unmount_callbacks_.empty())
+    return false;
+  while (!pending_unmount_callbacks_.empty()) {
+    pending_unmount_callbacks_.front().Run(chromeos::MOUNT_ERROR_NONE);
+    pending_unmount_callbacks_.pop();
+  }
+  return true;
 }
 
 void FakeDiskMountManager::FormatMountedDevice(const std::string& mount_path) {
 }
 
 void FakeDiskMountManager::UnmountDeviceRecursively(
     const std::string& device_path,
     const UnmountDeviceRecursivelyCallbackType& callback) {
 }
 
 bool FakeDiskMountManager::AddDiskForTest(std::unique_ptr<Disk> disk) {
   DCHECK(disk);
   return disks_.insert(make_pair(disk->device_path(), std::move(disk))).second;
 }
 
 bool FakeDiskMountManager::AddMountPointForTest(
     const MountPointInfo& mount_point) {
   return false;
 }
 
 void FakeDiskMountManager::InvokeDiskEventForTest(
     chromeos::disks::DiskMountManager::DiskEvent event,
     const chromeos::disks::DiskMountManager::Disk* disk) {
   FOR_EACH_OBSERVER(chromeos::disks::DiskMountManager::Observer,
                     observers_,
                     OnDiskEvent(event, disk));
 }
 
 }  // namespace file_manager