Omit a queue name in a "socket://" printer URI

Printer URIs with a "socket" protocol cannot have a path component.
However, our UI allows a user to provide a queue name (a path) for all
types of printers. Moreover, this field has a non-empty default value.
This causes a validation error of provided printer URIs with a "socket"
protocol when a user doesn't clean the field by hand. This patch solves
the problem by automatically removing a path component from provided
URI when the protocol is set to "socket".

BUG=chromium:1129047
TEST=tested on atlas

Change-Id: I92d8afbaaf4f0e74d102b1384ef7378d34b15496
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2423344
Commit-Queue: Piotr Pawliczek <pawliczek@chromium.org>
Auto-Submit: Piotr Pawliczek <pawliczek@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810072}

chrome/browser/ui/webui/settings/chromeos/cups_printers_handler.cc

@@ -147,10 +147,13 @@ std::unique_ptr<chromeos::Printer> DictToPrinter(
   }
 
   std::string printer_queue;
-  printer_dict.GetString("printerQueue", &printer_queue);
-  // Path must start from '/' character.
-  if (!printer_queue.empty() && printer_queue.front() != '/')
-    printer_queue = "/" + printer_queue;
+  // The protocol "socket" does not allow path.
+  if (printer_protocol != "socket") {
+    printer_dict.GetString("printerQueue", &printer_queue);
+    // Path must start from '/' character.
+    if (!printer_queue.empty() && printer_queue.front() != '/')
+      printer_queue.insert(0, "/");
+  }
 
   auto printer = std::make_unique<chromeos::Printer>(printer_id);
   printer->set_display_name(printer_name);