[usb_gadget p12] Basic tests of usb_service using the USB test gadget.

components/usb_service/usb_service_impl.cc

Index: components/usb_service/usb_service_impl.cc
diff --git a/components/usb_service/usb_service_impl.cc b/components/usb_service/usb_service_impl.cc
index 88aa98f676d5cfe7b5b05b6a5c33228e941132fe..a77749e7d4da3a245481aacbeb296bfe4e98ecaf 100644
--- a/components/usb_service/usb_service_impl.cc
+++ b/components/usb_service/usb_service_impl.cc
@@ -154,7 +154,6 @@ void UsbServiceImpl::RefreshDevices() {
 
 // static
 UsbService* UsbService::GetInstance() {
-  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::FILE));
   UsbService* instance = g_usb_service_instance.Get().get();
   if (!instance) {
     PlatformUsbContext context = NULL;
@@ -175,7 +174,6 @@ UsbService* UsbService::GetInstance() {
 
 // static
 void UsbService::SetInstanceForTest(UsbService* instance) {
-  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::FILE));
   g_usb_service_instance.Get().reset(instance);
 }