Add an autoconf field to printer objects.

chrome/browser/chromeos/printing/specifics_translation.h

Index: chrome/browser/chromeos/printing/specifics_translation.h
diff --git a/chrome/browser/chromeos/printing/specifics_translation.h b/chrome/browser/chromeos/printing/specifics_translation.h
index 382f766c3c7fec1253f1decdc23d154eacfa158a..386b944b5bdad9e145a4a85a861c9f5d00ae67ca 100644
--- a/chrome/browser/chromeos/printing/specifics_translation.h
+++ b/chrome/browser/chromeos/printing/specifics_translation.h
@@ -13,13 +13,21 @@
 namespace chromeos {
 namespace printing {
 
+// Convert |printer| into its local representation.  Enforces that only one
+// field in PpdReference is filled in.  In order of preference, we populate
+// autoconf, user_supplied_ppd_url, or effective_make_and_model.
 std::unique_ptr<Printer> SpecificsToPrinter(
     const sync_pb::PrinterSpecifics& printer);
 
+// Convert |printer| into its proto representation.
 std::unique_ptr<sync_pb::PrinterSpecifics> PrinterToSpecifics(
     const Printer& printer);
 
-// Merge fields from |printer| into |specifics|.
+// Merge fields from |printer| into |specifics|.  Merge strategy is to only
+// write non-default fields from |printer| into the appropriate field in
+// |specifics|.  Default fields are skipped to prevent accidentally clearing
+// |specifics|.  Enforces field exclusivity in PpdReference as described in
+// SpecificsToPrinter.
 void MergePrinterToSpecifics(const Printer& printer,
                              sync_pb::PrinterSpecifics* specifics);