Cleanup: Remove some std::map::operator[] usage in ApiResourceManager.

extensions/browser/api/usb/usb_device_resource.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 "extensions/browser/api/usb/usb_device_resource.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/lazy_instance.h"
 #include "base/synchronization/lock.h"
 #include "content/public/browser/browser_thread.h"
 #include "device/usb/usb_device_handle.h"
 #include "extensions/browser/api/api_resource.h"
 #include "extensions/common/api/usb.h"
 
 using content::BrowserThread;
 using device::UsbDeviceHandle;
 
 namespace extensions {
@@ skipping 16 matching lines @@
 
 UsbDeviceResource::~UsbDeviceResource() {
   device_->Close();
 }
 
 bool UsbDeviceResource::IsPersistent() const {
   return false;
 }
 
 }  // namespace extensions