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

chrome/browser/chromeos/file_manager/volume_manager_unittest.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/volume_manager.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <vector>
@@ skipping 704 matching lines @@
   volume_manager()->OnExternalStorageDisabledChanged();
 
   // Expect no effects.
   EXPECT_EQ(2U, disk_mount_manager_->mount_points().size());
   EXPECT_EQ(0U, disk_mount_manager_->unmount_requests().size());
 
   // Emulate to set kExternalStorageDisabled to true.
   profile()->GetPrefs()->SetBoolean(prefs::kExternalStorageDisabled, true);
   volume_manager()->OnExternalStorageDisabledChanged();
 
+  // Wait until all unmount request finishes, so that callback chain to unmount
+  // all the mount points will be invoked.
+  disk_mount_manager_->FinishAllUnmountPathRequests();
+
   // The all mount points should be unmounted.
   EXPECT_EQ(0U, disk_mount_manager_->mount_points().size());
 
   EXPECT_EQ(2U, disk_mount_manager_->unmount_requests().size());
   const FakeDiskMountManager::UnmountRequest& unmount_request1 =
       disk_mount_manager_->unmount_requests()[0];
   EXPECT_EQ("mount1", unmount_request1.mount_path);
 
   const FakeDiskMountManager::UnmountRequest& unmount_request2 =
       disk_mount_manager_->unmount_requests()[1];
@@ skipping 165 matching lines @@
   // Detach
   volume_manager()->OnRemovableStorageDetached(info);
   ASSERT_EQ(2u, observer.events().size());
   EXPECT_EQ(LoggingObserver::Event::VOLUME_UNMOUNTED,
             observer.events()[1].type);
 
   EXPECT_FALSE(volume.get());
 }
 
 }  // namespace file_manager