Added a diagnostic user message when enumerating printers fails. Also tweaked...

chrome/service/cloud_print/print_system_cups.cc

Index: chrome/service/cloud_print/print_system_cups.cc
===================================================================
--- chrome/service/cloud_print/print_system_cups.cc	(revision 72042)
+++ chrome/service/cloud_print/print_system_cups.cc	(working copy)
@@ -13,6 +13,7 @@
 #include <list>
 #include <map>
 
+#include "app/l10n_util.h"
 #include "base/file_path.h"
 #include "base/json/json_reader.h"
 #include "base/lock.h"
@@ -29,6 +30,7 @@
 #include "chrome/service/cloud_print/cloud_print_consts.h"
 #include "chrome/service/cloud_print/cloud_print_helpers.h"
 #include "googleurl/src/gurl.h"
+#include "grit/generated_resources.h"
 #include "printing/backend/cups_helper.h"
 #include "printing/backend/print_backend.h"
 #include "printing/backend/print_backend_consts.h"
@@ -74,7 +76,8 @@
   // PrintSystem implementation.
   virtual PrintSystemResult Init();
 
-  virtual void EnumeratePrinters(printing::PrinterList* printer_list);
+  virtual PrintSystem::PrintSystemResult EnumeratePrinters(
+      printing::PrinterList* printer_list);
 
   virtual void GetPrinterCapsAndDefaults(
       const std::string& printer_name,
@@ -152,6 +155,9 @@
 
   int update_timeout_;
   bool initialized_;
+  // A comma separated string of print server names for which enumeration of
+  // printers failed. This is used to prepare a diagnostic error message.
+  std::string enum_failed_server_list_;
 };
 
 class PrintServerWatcherCUPS
@@ -413,8 +419,12 @@
 
 void PrintSystemCUPS::UpdatePrinters() {
   PrintServerList::iterator it;
+  enum_failed_server_list_.clear();
   for (it = print_servers_.begin(); it != print_servers_.end(); ++it) {
-    it->backend->EnumeratePrinters(&it->printers);
+    if (!it->backend->EnumeratePrinters(&it->printers)) {
+      enum_failed_server_list_.append(it->url.spec());
+      enum_failed_server_list_.append(",");
+    }
     it->caps_cache.clear();
     printing::PrinterList::iterator printer_it;
     for (printer_it = it->printers.begin();
@@ -432,7 +442,8 @@
       GetUpdateTimeoutMs());
 }
 
-void PrintSystemCUPS::EnumeratePrinters(printing::PrinterList* printer_list) {
+PrintSystem::PrintSystemResult PrintSystemCUPS::EnumeratePrinters(
+    printing::PrinterList* printer_list) {
   DCHECK(initialized_);
   printer_list->clear();
   PrintServerList::iterator it;
@@ -441,6 +452,13 @@
         it->printers.begin(), it->printers.end());
   }
   VLOG(1) << "CUPS: Total " << printer_list->size() << " printers enumerated.";
+  if (!enum_failed_server_list_.empty()) {
+    // The enumeration failed on some servers.
+    // TODO(sanjeevr): Maybe some day we want to report the actual server names.
+    std::string message = l10n_util::GetStringUTF8(IDS_CLOUD_PRINT_ENUM_FAILED);
+    return PrintSystemResult(false, message);
+  }
+  return PrintSystemResult(true, std::string());
 }
 
 void PrintSystemCUPS::GetPrinterCapsAndDefaults(