Cache important USB string descriptors all at once.

device/usb/usb_device_impl.h

 // 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.
 
 #ifndef DEVICE_USB_USB_DEVICE_IMPL_H_
 #define DEVICE_USB_USB_DEVICE_IMPL_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 38 matching lines @@
   // Called by UsbServiceImpl only;
   UsbDeviceImpl(scoped_refptr<UsbContext> context,
                 scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
                 PlatformUsbDevice platform_device,
                 uint16 vendor_id,
                 uint16 product_id,
                 uint32 unique_id);
 
   virtual ~UsbDeviceImpl();
 
-  // Called only be UsbService.
+  // Called only by UsbService.
   void OnDisconnect();
 
  private:
   base::ThreadChecker thread_checker_;
   PlatformUsbDevice platform_device_;
 
-#if defined(USE_UDEV)
   // On Linux these properties are read from sysfs when the device is enumerated
   // to avoid hitting the permission broker on Chrome OS for a real string
   // descriptor request.
-  std::string manufacturer_;
-  std::string product_;
-  std::string serial_number_;
+  base::string16 manufacturer_;
+  base::string16 product_;
+  base::string16 serial_number_;
+#if !defined(USE_UDEV)
+  // On other platforms the device must be opened in order to cache them. This
+  // should be delayed until the strings are needed to avoid poor interactions
+  // with other applications.
+  void CacheStrings();
+  bool strings_cached_;
 #endif
 
   // 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_;
 
   // Opened handles.
   typedef std::vector<scoped_refptr<UsbDeviceHandleImpl> > HandlesVector;
   HandlesVector handles_;
 
   // Reference to the UI thread for permission-broker calls.
   scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbDeviceImpl);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_USB_USB_DEVICE_IMPL_H_