Printing: Convert several wstrings to string16.

printing/printing_context.h

Index: printing/printing_context.h
diff --git a/printing/printing_context.h b/printing/printing_context.h
index 9f915a13a0881b923b6823a0b9a979ed7135cb94..eb1b0c781c26a73a1d0fc25cdd79a556b666ce66 100644
--- a/printing/printing_context.h
+++ b/printing/printing_context.h
@@ -20,6 +20,7 @@
 #include "base/logging.h"
 #endif
 #include "base/scoped_ptr.h"
+#include "base/string16.h"
 #include "gfx/native_widget_types.h"
 #include "printing/print_settings.h"
 
@@ -92,7 +93,7 @@ class PrintingContext {
   // like IPC message processing! Some printers have side-effects on this call
   // like virtual printers that ask the user for the path of the saved document;
   // for example a PDF printer.
-  Result NewDocument(const std::wstring& document_name);
+  Result NewDocument(const string16& document_name);
 
   // Starts a new page.
   Result NewPage();