Fix initial USB enumeration on Linux to return all devices.

device/usb/usb_service_linux.cc

Index: device/usb/usb_service_linux.cc
diff --git a/device/usb/usb_service_linux.cc b/device/usb/usb_service_linux.cc
index fdd4f89e58e5716785cb5c53c8200b2b961d6008..9f92cbb463afdbc58102a362a63ad270c4816d0b 100644
--- a/device/usb/usb_service_linux.cc
+++ b/device/usb/usb_service_linux.cc
@@ -248,7 +248,8 @@ void UsbServiceLinux::DeviceReady(scoped_refptr<UsbDeviceLinux> device,
   bool enumeration_became_ready = false;
   if (!enumeration_ready()) {
     DCHECK_GT(first_enumeration_countdown_, 0u);
-    if (--first_enumeration_countdown_ == 0)
+    first_enumeration_countdown_--;
+    if (enumeration_ready())
       enumeration_became_ready = true;
   }