Replace OVERRIDE with its C++11 counterparts in src/printing

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 c206d51b0f1e52897f6a2ba923011d4ae0f4f003..2e91fb19dfc1244a130a80b1489748be4169c8bd 100644
--- a/printing/backend/print_backend_chromeos.cc
+++ b/printing/backend/print_backend_chromeos.cc
@@ -14,17 +14,17 @@ class PrintBackendChromeOS : public PrintBackend {
   PrintBackendChromeOS();
 
   // PrintBackend implementation.
-  virtual bool EnumeratePrinters(PrinterList* printer_list) OVERRIDE;
-  virtual std::string GetDefaultPrinterName() OVERRIDE;
+  virtual bool EnumeratePrinters(PrinterList* printer_list) override;
+  virtual std::string GetDefaultPrinterName() override;
   virtual bool GetPrinterSemanticCapsAndDefaults(
       const std::string& printer_name,
-      PrinterSemanticCapsAndDefaults* printer_info) OVERRIDE;
+      PrinterSemanticCapsAndDefaults* printer_info) override;
   virtual bool GetPrinterCapsAndDefaults(
       const std::string& printer_name,
-      PrinterCapsAndDefaults* printer_info) OVERRIDE;
+      PrinterCapsAndDefaults* printer_info) override;
   virtual std::string GetPrinterDriverInfo(
-      const std::string& printer_name) OVERRIDE;
-  virtual bool IsValidPrinter(const std::string& printer_name) OVERRIDE;
+      const std::string& printer_name) override;
+  virtual bool IsValidPrinter(const std::string& printer_name) override;
 
  protected:
   virtual ~PrintBackendChromeOS() {}