[CUPS] Implement the Webui handler for the printers auto discovery.

chromeos/printing/fake_printer_discoverer.cc

Index: chromeos/printing/fake_printer_discoverer.cc
diff --git a/chromeos/printing/fake_printer_discoverer.cc b/chromeos/printing/fake_printer_discoverer.cc
index 5d8a298b4df7c888d3ace92d5c4c997bcd9be41e..3b41c03b911bd20c5890f479ccad7ab544b17deb 100644
--- a/chromeos/printing/fake_printer_discoverer.cc
+++ b/chromeos/printing/fake_printer_discoverer.cc
@@ -74,7 +74,7 @@ FakePrinterDiscoverer::FakePrinterDiscoverer()
 }
 
 void FakePrinterDiscoverer::EmitPrinters(size_t start, size_t end) {
-  if (!discovery_running_ || start >= printers_.size() || end > start)
+  if (!discovery_running_ || start >= printers_.size() || end < start)
     return;
 
   size_t clipped_start = std::max(static_cast<size_t>(0), start);