Convert device::UsbConfigDescriptor and friends to structs.

device/usb/usb_device_impl.h

Index: device/usb/usb_device_impl.h
diff --git a/device/usb/usb_device_impl.h b/device/usb/usb_device_impl.h
index 1ece2e0b17e784ba9803e9032ba4c0ad24106828..e95c8dbc9add72a27033e2a7da9300b4a82d493b 100644
--- a/device/usb/usb_device_impl.h
+++ b/device/usb/usb_device_impl.h
@@ -10,6 +10,7 @@
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/threading/thread_checker.h"
+#include "device/usb/usb_descriptors.h"
 #include "device/usb/usb_device.h"
 
 struct libusb_device;
@@ -37,7 +38,7 @@ class UsbDeviceImpl : public UsbDevice {
 #endif  // OS_CHROMEOS
   virtual scoped_refptr<UsbDeviceHandle> Open() OVERRIDE;
   virtual bool Close(scoped_refptr<UsbDeviceHandle> handle) OVERRIDE;
-  virtual scoped_refptr<UsbConfigDescriptor> ListInterfaces() OVERRIDE;
+  virtual const UsbConfigDescriptor& GetConfiguration() OVERRIDE;
 
  protected:
   friend class UsbServiceImpl;
@@ -59,6 +60,11 @@ class UsbDeviceImpl : public UsbDevice {
   base::ThreadChecker thread_checker_;
   PlatformUsbDevice platform_device_;
 
+  // The active configuration descriptor is not read immediately but cached for
+  // later use.
+  bool current_configuration_cached_;
+  UsbConfigDescriptor current_configuration_;
+
   // Retain the context so that it will not be released before UsbDevice.
   scoped_refptr<UsbContext> context_;