Added PrinterDriverInfo and PrintBackend::GetPrinterDriverInfo for windows.

printing/backend/win_helper.h

Index: printing/backend/win_helper.h
diff --git a/printing/backend/win_helper.h b/printing/backend/win_helper.h
index a08e69ac068557011ed4ef76205a992f5935a4f7..8e65aca4add8ae9e85acb8b57c727275f79c60e4 100644
--- a/printing/backend/win_helper.h
+++ b/printing/backend/win_helper.h
@@ -12,11 +12,22 @@
 #include <xpsprint.h>
 
 #include "base/string16.h"
+#include "base/win/scoped_handle.h"
 #include "printing/printing_export.h"
 
 // These are helper functions for dealing with Windows Printing.
 namespace printing {
 
+class PrinterHandleTraits {
+ public:
+  static bool CloseHandle(HANDLE handle) {
+    return ::ClosePrinter(handle) != FALSE;
+  }
+};
+
+typedef base::win::GenericScopedHandle<PrinterHandleTraits> ScopedPrinterHandle;
+
+
 // Wrapper class to wrap the XPS APIs (PTxxx APIs). This is needed because these
 // APIs are not available by default on XP. We could delayload prntvpt.dll but
 // this would mean having to add that to every binary that links with