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 56ad14929c27362fb00ab788b66d33193e0b4206..c94bb276a8429fdeb2110e48bcad0348117000a9 100644
--- a/device/usb/usb_service_linux.cc
+++ b/device/usb/usb_service_linux.cc
@@ -253,7 +253,8 @@ 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;
   }