Implement basic USB setup in the cups printer detector. Factor out

chrome/browser/chromeos/printing/usb_util.h

+// Copyright 2017 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.
+
+// Utility routines for working with UsbDevices that are printers.
+
+#ifndef CHROME_BROWSER_CHROMEOS_PRINTING_USB_UTIL_H__
+#define CHROME_BROWSER_CHROMEOS_PRINTING_USB_UTIL_H__

[stevenjb, 2017/03/17 17:34:11]

nit: Even though this is in chromeos/printing, it would be helpful for
discoverability to name the file something like usb_printer_util.

[Carlson, 2017/03/17 18:47:34]

Done.

+
+#include <memory>
+#include <string>
+
+#include "base/memory/ref_counted.h"
+
+namespace device {
+class UsbDevice;
+}
+
+namespace chromeos {
+
+class Printer;
+
+bool UsbDeviceIsPrinter(scoped_refptr<device::UsbDevice> usb_device);
+
+// Convert the interesting details of a device to a string, for
+// logging/debugging.
+std::string UsbPrinterDeviceDetailsAsString(const device::UsbDevice& device);
+
+// Attempt to gather all the information we need to work with this printer by
+// querying the USB device.  This should only be called using devices we believe
+// are printers, not arbitrary USB devices, as we may get weird partial results
+// from arbitrary devices.
+//
+// Returns nullptr and logs an error on failure.
+std::unique_ptr<Printer> UsbDeviceToPrinter(const device::UsbDevice& device);
+
+// Gets the URI CUPS would use to refer to this USB device.  Assumes device
+// is a printer.
+std::string UsbPrinterUri(const device::UsbDevice& device);
+
+}  // namespace chromeos
+#endif  // CHROME_BROWSER_CHROMEOS_PRINTING_USB_UTIL_H__