Log errors from libusb.

components/usb_service/usb_context.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 "components/usb_service/usb_context.h"
 
 #include "base/logging.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/platform_thread.h"
+#include "components/usb_service/usb_error.h"
 #include "third_party/libusb/src/libusb/interrupt.h"
 #include "third_party/libusb/src/libusb/libusb.h"
 
 namespace usb_service {
 
 // The UsbEventHandler works around a design flaw in the libusb interface. There
 // is currently no way to signal to libusb that any caller into one of the event
 // handler calls should return without handling any events.
 class UsbContext::UsbEventHandler : public base::PlatformThread::Delegate {
  public:
@@ skipping 27 matching lines @@
   base::subtle::MemoryBarrier();
   libusb_interrupt_handle_event(context_);
   base::PlatformThread::Join(thread_handle_);
 }
 
 void UsbContext::UsbEventHandler::ThreadMain() {
   base::PlatformThread::SetName("UsbEventHandler");
   VLOG(1) << "UsbEventHandler started.";
   if (running_) {
     start_polling_.Signal();
-    libusb_handle_events(context_);
   }
-  while (running_)
-    libusb_handle_events(context_);
+  while (running_) {
+    const int rv = libusb_handle_events(context_);
+    if (rv != LIBUSB_SUCCESS) {
+      LOG(WARNING) << "Failed to handle events: " << ConvertErrorToString(rv);
+    }
+  }
   VLOG(1) << "UsbEventHandler shutting down.";
 }
 
 UsbContext::UsbContext(PlatformUsbContext context) : context_(context) {
   DCHECK(thread_checker_.CalledOnValidThread());
   event_handler_ = new UsbEventHandler(context_);
 }
 
 UsbContext::~UsbContext() {
   // destruction of UsbEventHandler is a blocking operation.
   DCHECK(thread_checker_.CalledOnValidThread());
   delete event_handler_;
   event_handler_ = NULL;
   libusb_exit(context_);
 }
 
 }  // namespace usb_service