Present the printer list from preferences for Chrome OS.

chrome/browser/ui/webui/print_preview/print_preview_handler.cc

Index: chrome/browser/ui/webui/print_preview/print_preview_handler.cc
diff --git a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
index 1119b974cb21344b9e07167d50ae48668930743d..35364c1787a90bcb550c4c6942e2ca3e59180652 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
+++ b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
@@ -49,6 +49,7 @@
 #include "chrome/browser/ui/chrome_select_file_policy.h"
 #include "chrome/browser/ui/scoped_tabbed_browser_displayer.h"
 #include "chrome/browser/ui/webui/print_preview/print_preview_ui.h"
+#include "chrome/browser/ui/webui/print_preview/printer_backend_proxy.h"
 #include "chrome/browser/ui/webui/print_preview/printer_handler.h"
 #include "chrome/browser/ui/webui/print_preview/sticky_settings.h"
 #include "chrome/common/chrome_switches.h"
@@ -294,17 +295,6 @@ void PrintToPdfCallback(const scoped_refptr<base::RefCountedBytes>& data,
     pdf_file_saved_closure.Run();
 }
 
-std::string GetDefaultPrinterOnBlockingPoolThread() {
-  DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
-
-  scoped_refptr<printing::PrintBackend> print_backend(
-      printing::PrintBackend::CreateInstance(nullptr));
-
-  std::string default_printer = print_backend->GetDefaultPrinterName();
-  VLOG(1) << "Default Printer: " << default_printer;
-  return default_printer;
-}
-
 class PrintingContextDelegate : public printing::PrintingContext::Delegate {
  public:
   // PrintingContext::Delegate methods.
@@ -393,21 +383,18 @@ std::pair<std::string, std::string> GetPrinterNameAndDescription(
   if (it != printer.options.end())
     real_description = it->second;
   return std::make_pair(real_name, real_description);
+#elif defined(OS_CHROMEOS)
+  // For Chrome OS |printer.printer_display_name| is the human readable name and

[Lei Zhang, 2016/11/03 07:39:50]

So is ChromeOS more in line with Mac then? Maybe don't add a ChromeOS-only
"printer_display_name" field to PrinterBasicInfo, and just create the info the
Mac way in ToBasicInfo() ?

Having 2 different ways to interpret PrinterBasicInfo is already a bit
confusing. Let's not expand it to 3 ways.

[skau, 2016/11/03 21:58:27]

Per discussion, I'm going to try to align all the platforms around
printer_display_name.  But the interest of time, ChromeOS will take the OS X
code path as well.

[Lei Zhang, 2016/11/03 22:06:12]

Agreed, I think that's a safer bet.

+  // |printer.printer_name| is the name used in CUPS.
+  return std::make_pair(printer.printer_display_name,
+                        printer.printer_description);
 #else
   return std::make_pair(printer.printer_name, printer.printer_description);
 #endif
 }
 
-void EnumeratePrintersOnBlockingPoolThread(base::ListValue* printers) {
-  DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
-
-  scoped_refptr<printing::PrintBackend> print_backend(
-      printing::PrintBackend::CreateInstance(nullptr));
-
-  VLOG(1) << "Enumerate printers start";
-  printing::PrinterList printer_list;
-  print_backend->EnumeratePrinters(&printer_list);
-
+void PrintersToValues(const printing::PrinterList& printer_list,
+                      base::ListValue* printers) {
   for (const printing::PrinterBasicInfo& printer : printer_list) {
     std::unique_ptr<base::DictionaryValue> printer_info(
         new base::DictionaryValue);
@@ -429,6 +416,15 @@ void EnumeratePrintersOnBlockingPoolThread(base::ListValue* printers) {
     VLOG(1) << "Found printer " << printer_name << " with device name "
             << printer.printer_name;
   }
+}
+
+void EnumeratePrinters(Profile* profile, base::ListValue* printers) {
+  DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+
+  VLOG(1) << "Enumerate printers start";
+  printing::PrinterList printer_list =
+      printing::EnumeratePrintersOnBlockingPoolThread(profile);
+  PrintersToValues(printer_list, printers);
   VLOG(1) << "Enumerate printers finished, found " << printers->GetSize()
           << " printers";
 }
@@ -688,7 +684,7 @@ PrintPreviewUI* PrintPreviewHandler::print_preview_ui() const {
 void PrintPreviewHandler::HandleGetPrinters(const base::ListValue* /*args*/) {
   base::ListValue* results = new base::ListValue;
   BrowserThread::PostBlockingPoolTaskAndReply(
-      FROM_HERE, base::Bind(&EnumeratePrintersOnBlockingPoolThread,
+      FROM_HERE, base::Bind(&EnumeratePrinters, Profile::FromWebUI(web_ui()),
                             base::Unretained(results)),
       base::Bind(&PrintPreviewHandler::SetupPrinterList,
                  weak_factory_.GetWeakPtr(), base::Owned(results)));
@@ -1224,7 +1220,7 @@ void PrintPreviewHandler::HandleGetInitialSettings(
   SendCloudPrintEnabled();
   base::PostTaskAndReplyWithResult(
       BrowserThread::GetBlockingPool(), FROM_HERE,
-      base::Bind(&GetDefaultPrinterOnBlockingPoolThread),
+      base::Bind(&printing::GetDefaultPrinterOnBlockingPoolThread),
       base::Bind(&PrintPreviewHandler::SendInitialSettings,
                  weak_factory_.GetWeakPtr()));
 }