Add a PrinterDiscoverer fake object.

chromeos/printing/fake_printer_discoverer.h

Index: chromeos/printing/fake_printer_discoverer.h
diff --git a/chromeos/printing/fake_printer_discoverer.h b/chromeos/printing/fake_printer_discoverer.h
new file mode 100644
index 0000000000000000000000000000000000000000..bbc61bb53b080b7184b4832ee44834a6f55d0c23
--- /dev/null
+++ b/chromeos/printing/fake_printer_discoverer.h
@@ -0,0 +1,41 @@
+// Copyright 2016 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 CHROMEOS_PRINTING_FAKE_PRINTER_DISCOVERER_H_
+#define CHROMEOS_PRINTING_FAKE_PRINTER_DISCOVERER_H_
+
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "chromeos/printing/printer_configuration.h"
+#include "chromeos/printing/printer_discoverer.h"
+
+namespace chromeos {
+
+class FakePrinterDiscoverer : public PrinterDiscoverer {
+ public:
+  FakePrinterDiscoverer();
+  ~FakePrinterDiscoverer();
+
+  bool StartDiscovery() override;
+  bool StopDiscovery() override;
+  void AddObserver(PrinterDiscoverer::Observer* observer) override;
+  void RemoveObserver(PrinterDiscoverer::Observer* observer) override;
+
+ private:
+  void EmitPrinters(size_t start, size_t end);
+
+  std::vector<chromeos::Printer> printers_;
+  bool discovery_running_;
+  std::vector<PrinterDiscoverer::Observer*> observers_;
+
+  base::WeakPtrFactory<FakePrinterDiscoverer> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(FakePrinterDiscoverer);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROMEOS_PRINTING_FAKE_PRINTER_DISCOVERER_H_