Add API tests for the chrome.hid API.

device/hid/hid_service.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 "device/hid/hid_service.h"
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/scoped_vector.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 37 matching lines @@
     scoped_refptr<base::SingleThreadTaskRunner> file_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner) {
   if (g_service == NULL) {
 #if defined(OS_LINUX) && defined(USE_UDEV)
     g_service = new HidServiceLinux(ui_task_runner);
 #elif defined(OS_MACOSX)
     g_service = new HidServiceMac(file_task_runner);
 #elif defined(OS_WIN)
     g_service = new HidServiceWin();
 #endif
-    if (g_service != NULL) {
+    if (g_service != nullptr) {
       Destroyer* destroyer = new Destroyer(g_service);
       base::MessageLoop::current()->AddDestructionObserver(destroyer);
     }
   }
   return g_service;
 }
 
+void HidService::SetInstanceForTest(HidService* instance) {
+  DCHECK(!g_service);
+  g_service = instance;
+  Destroyer* destroyer = new Destroyer(g_service);
+  base::MessageLoop::current()->AddDestructionObserver(destroyer);
+}
+
 HidService::~HidService() {
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
 void HidService::GetDevices(std::vector<HidDeviceInfo>* devices) {
   DCHECK(thread_checker_.CalledOnValidThread());
   STLClearObject(devices);
   for (DeviceMap::iterator it = devices_.begin();
       it != devices_.end();
       ++it) {
@@ skipping 23 matching lines @@
 }
 
 void HidService::RemoveDevice(const HidDeviceId& device_id) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DeviceMap::iterator it = devices_.find(device_id);
   if (it != devices_.end())
     devices_.erase(it);
 }
 
 }  // namespace device