Observe UsbService from the FILE thread in DevicePermissionsManager.

chrome/browser/extensions/api/device_permissions_manager_unittest.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 "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/values_test_util.h"
 #include "chrome/browser/extensions/test_extension_environment.h"
 #include "chrome/test/base/testing_profile.h"
 #include "device/core/device_client.h"
@@ skipping 205 matching lines @@
   // ExtensionPrefs, it is "persistent".
   ASSERT_TRUE(FindEntry(device_permissions.get(), device0_).get());
   // Device 1 does not have uniquely identifying traits and so permission to
   // open it has been dropped when the app's windows have closed and the
   // background page has been suspended.
   ASSERT_FALSE(FindEntry(device_permissions.get(), device1_).get());
   ASSERT_FALSE(FindEntry(device_permissions.get(), device2_).get());
   ASSERT_FALSE(FindEntry(device_permissions.get(), device3_).get());
 }
 
-TEST_F(DevicePermissionsManagerTest, DisconnectDevice) {
+// TODO(reillyg): Until crbug.com/427985 is resolved device removal
+// notifications are delivered asynchronously and so this test must be disabled.
+TEST_F(DevicePermissionsManagerTest, DISABLED_DisconnectDevice) {
   DevicePermissionsManager* manager =
       DevicePermissionsManager::Get(env_.profile());
   AllowUsbDevice(manager, extension_, device0_);
   AllowUsbDevice(manager, extension_, device1_);
 
   scoped_ptr<DevicePermissions> device_permissions =
       manager->GetForExtension(extension_->id());
   ASSERT_TRUE(FindEntry(device_permissions.get(), device0_).get());
   ASSERT_TRUE(FindEntry(device_permissions.get(), device1_).get());
   ASSERT_FALSE(FindEntry(device_permissions.get(), device2_).get());
@@ skipping 84 matching lines @@
       DevicePermissionsManager::Get(env_.profile());
   scoped_ptr<DevicePermissions> device_permissions =
       manager->GetForExtension(extension_->id());
   ASSERT_TRUE(FindEntry(device_permissions.get(), device0_).get());
   ASSERT_FALSE(FindEntry(device_permissions.get(), device1_).get());
   ASSERT_FALSE(FindEntry(device_permissions.get(), device2_).get());
   ASSERT_FALSE(FindEntry(device_permissions.get(), device3_).get());
 }
 
 }  // namespace extensions