Extract //device/usb mocks so that they can be shared.

device/usb/mock_usb_service.cc

+// Copyright 2015 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 "device/usb/mock_usb_service.h"
+
+#include "device/usb/usb_device.h"
+
+namespace device {
+
+MockUsbService::MockUsbService() {
+}
+
+MockUsbService::~MockUsbService() {
+}
+
+void MockUsbService::AddDevice(scoped_refptr<UsbDevice> device) {
+  devices_[device->unique_id()] = device;
+  NotifyDeviceAdded(device);
+}
+
+void MockUsbService::RemoveDevice(scoped_refptr<UsbDevice> device) {
+  devices_.erase(device->unique_id());
+  UsbService::NotifyDeviceRemoved(device);
+}
+
+scoped_refptr<UsbDevice> MockUsbService::GetDeviceById(uint32 unique_id) {
+  auto it = devices_.find(unique_id);
+  EXPECT_TRUE(it != devices_.end());
+  return it->second;
+}
+
+void MockUsbService::GetDevices(const GetDevicesCallback& callback) {
+  std::vector<scoped_refptr<UsbDevice>> devices;
+  for (const auto& map_entry : devices_) {
+    devices.push_back(map_entry.second);
+  }
+  callback.Run(devices);
+}
+
+}  // namespace device