Change getExtensionPrinters to cr.sendWithPromise

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

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/print_preview/print_preview_handler.h"
 
 #include <ctype.h>
 #include <stddef.h>
 
 #include <map>
@@ skipping 691 matching lines @@
   DCHECK(success);
 
   CreatePrivetHTTP(
       name, base::Bind(&PrintPreviewHandler::PrivetCapabilitiesUpdateClient,
                        weak_factory_.GetWeakPtr()));
 #endif
 }
 
 void PrintPreviewHandler::HandleGetExtensionPrinters(
     const base::ListValue* args) {
+  std::string callback_id;
+  CHECK(args->GetString(0, &callback_id));
+  CHECK(!callback_id.empty());
+
+  AllowJavascript();
   EnsureExtensionPrinterHandlerSet();
   // Make sure all in progress requests are canceled before new printer search
   // starts.
   extension_printer_handler_->Reset();
   extension_printer_handler_->StartGetPrinters(
       base::Bind(&PrintPreviewHandler::OnGotPrintersForExtension,
-                 weak_factory_.GetWeakPtr()));
+                 weak_factory_.GetWeakPtr(), callback_id));
 }
 
 void PrintPreviewHandler::HandleGrantExtensionPrinterAccess(
     const base::ListValue* args) {
   std::string printer_id;
   bool ok = args->GetString(0, &printer_id);
   DCHECK(ok);
 
   EnsureExtensionPrinterHandlerSet();
   extension_printer_handler_->StartGrantPrinterAccess(
@@ skipping 999 matching lines @@
 
 void PrintPreviewHandler::EnsureExtensionPrinterHandlerSet() {
   if (extension_printer_handler_)
     return;
 
   extension_printer_handler_ =
       PrinterHandler::CreateForExtensionPrinters(Profile::FromWebUI(web_ui()));
 }
 
 void PrintPreviewHandler::OnGotPrintersForExtension(
+    const std::string& callback_id,
     const base::ListValue& printers,
     bool done) {
-  web_ui()->CallJavascriptFunctionUnsafe("onExtensionPrintersAdded", printers,
-                                         base::Value(done));
+  AllowJavascript();
+
+  FireWebUIListener("extension-printers-added", printers);
+  if (done) {
+    ResolveJavascriptCallback(base::Value(callback_id), base::Value(true));

[dpapad, 2017/06/07 03:20:11]

Is the boolean passed here needed? It seems that we only ever pass "true", so
seems unnecessary.

[rbpotter, 2017/06/07 03:46:42]

Done.

+  }
 }
 
 void PrintPreviewHandler::OnGotExtensionPrinterInfo(
     const std::string& printer_id,
     const base::DictionaryValue& printer_info) {
   if (printer_info.empty()) {
     web_ui()->CallJavascriptFunctionUnsafe("failedToResolveProvisionalPrinter",
                                            base::Value(printer_id));
     return;
   }
@@ skipping 42 matching lines @@
 
 void PrintPreviewHandler::UnregisterForGaiaCookieChanges() {
   if (gaia_cookie_manager_service_)
     gaia_cookie_manager_service_->RemoveObserver(this);
 }
 
 void PrintPreviewHandler::SetPdfSavedClosureForTesting(
     const base::Closure& closure) {
   pdf_file_saved_closure_ = closure;
 }