Printing: Add ability to get the default printer from the print backend.

printing/backend/print_backend_cups.cc

 // Copyright (c) 2010 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.
 
 #include "printing/backend/print_backend.h"
 
 #include <dlfcn.h>
 #include <errno.h>
 #if !defined(OS_MACOSX)
 #include <gcrypt.h>
@@ skipping 68 matching lines @@
 static const char kCUPSPrinterStateOpt[] = "printer-state";
 
 class PrintBackendCUPS : public PrintBackend {
  public:
   PrintBackendCUPS(const GURL& print_server_url, bool blocking);
   virtual ~PrintBackendCUPS() {}
 
   // PrintBackend implementation.
   virtual bool EnumeratePrinters(PrinterList* printer_list);
 
+  virtual std::string GetDefaultPrinterName();
+
   virtual bool GetPrinterCapsAndDefaults(const std::string& printer_name,
                                          PrinterCapsAndDefaults* printer_info);
 
   virtual bool IsValidPrinter(const std::string& printer_name);
 
  private:
   // Following functions are wrappers around corresponding CUPS functions.
   // <functions>2()  are called when print server is specified, and plain
   // version in another case. There is an issue specifing CUPS_HTTP_DEFAULT
   // in the <functions>2(), it does not work in CUPS prior to 1.4.
@@ skipping 47 matching lines @@
 
     printer_list->push_back(printer_info);
   }
 
   cupsFreeDests(num_dests, destinations);
 
   VLOG(1) << "CUPS: Enumerated " << printer_list->size() << " printers.";
   return true;
 }
 
+std::string PrintBackendCUPS::GetDefaultPrinterName() {
+  // TODO(thestig) Figure out why cupsGetDefault() lies about the default
+  // printer. :-(
+  // Return an empty string for now.
+  return std::string();
+}
+
 bool PrintBackendCUPS::GetPrinterCapsAndDefaults(
     const std::string& printer_name,
     PrinterCapsAndDefaults* printer_info) {
   DCHECK(printer_info);
 
   VLOG(1) << "CUPS: Getting Caps and Defaults for: " << printer_name;
 
   FilePath ppd_path(GetPPD(printer_name.c_str()));
   // In some cases CUPS failed to get ppd file.
   if (ppd_path.empty()) {
@@ skipping 102 matching lines @@
                    << ", HTTP error: " << http_error;
         file_util::Delete(ppd_path, false);
         ppd_path.clear();
       }
     }
   }
   return ppd_path;
 }
 
 }  // namespace printing