Fixed return value.

printing/backend/print_backend_chromeos.cc

Index: printing/backend/print_backend_chromeos.cc
diff --git a/printing/backend/print_backend_chromeos.cc b/printing/backend/print_backend_chromeos.cc
index a70516c071162379376c8c8af989801b891f82ed..767251c638b79e5efba7ed5913899663e135f6da 100644
--- a/printing/backend/print_backend_chromeos.cc
+++ b/printing/backend/print_backend_chromeos.cc
@@ -44,10 +44,10 @@ bool PrintBackendChromeOS::GetPrinterCapsAndDefaults(
   return false;
 }
 
-std::string  PrintBackendChromeOS::GetPrinterDriverInfo(
+std::string PrintBackendChromeOS::GetPrinterDriverInfo(
     const std::string& printer_name) {
   NOTREACHED();
-  return false;
+  return std::string();
 }
 
 std::string PrintBackendChromeOS::GetDefaultPrinterName() {