Fail gracefully when libusb_init fails

chrome/browser/usb/usb_service.cc

Index: chrome/browser/usb/usb_service.cc
diff --git a/chrome/browser/usb/usb_service.cc b/chrome/browser/usb/usb_service.cc
index b44c1fa0136871e2492564da77d2312348ee8b4f..8cd33689288f3a1c304d6c67bc81e783c94ba6c3 100644
--- a/chrome/browser/usb/usb_service.cc
+++ b/chrome/browser/usb/usb_service.cc
@@ -64,8 +64,8 @@ class ExitObserver : public content::NotificationObserver {
 
 using content::BrowserThread;
 
-UsbService::UsbService()
-    : context_(new UsbContext()),
+UsbService::UsbService(PlatformUsbContext context)
+    : context_(new UsbContext(context)),
       next_unique_id_(0) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   // Will be deleted upon NOTIFICATION_APP_TERMINATING.
@@ -79,10 +79,21 @@ UsbService::~UsbService() {
   }
 }
 
+struct InitUsbContextTraits : public LeakySingletonTraits<UsbService> {
+  // LeakySingletonTraits<UsbService>
+  static UsbService* New() {
+    PlatformUsbContext context;
+    libusb_init(&context);
+    if (!context)

[xiyuan, 2013/09/04 20:22:22]

nit: should we check the return code of libusb_init instead of relying on it to
nullify |context|?

[Bei Zhang, 2013/09/04 21:04:58]

I see. There's chance that context is not even initialized.

On 2013/09/04 20:22:22, xiyuan wrote:

+      return NULL;
+    return new UsbService(context);
+  }
+};
+
 UsbService* UsbService::GetInstance() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   // UsbService deletes itself upon APP_TERMINATING.
-  return Singleton<UsbService, LeakySingletonTraits<UsbService> >::get();
+  return Singleton<UsbService, InitUsbContextTraits>::get();
 }
 
 void UsbService::GetDevices(std::vector<scoped_refptr<UsbDevice> >* devices) {