Print Preview: Use cr.sendWithPromise for getInitialSettings

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 0f0bde1698ffb13967aaf4c507c063f10e8e190e..6b23950c7212ad16c34c00059ec97a3523b582e3 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
+++ b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
@@ -1208,11 +1208,19 @@ void PrintPreviewHandler::GetNumberFormatAndMeasurementSystem(
 }
 
 void PrintPreviewHandler::HandleGetInitialSettings(
-    const base::ListValue* /*args*/) {
+    const base::ListValue* args) {
+  AllowJavascript();
+
+  std::string callback_id;
+  if (!args->GetString(0, &callback_id) || callback_id.empty()) {

[dpapad, 2017/05/17 23:59:12]

If we get in here, that would be a programmer's error, right? Can we use an
assertion CHECK or DCHECK instead? See example
https://cs.chromium.org/chromium/src/chrome/browser/ui/webui/settings/languag....

[rbpotter, 2017/05/18 17:56:30]

Done.

+    RejectJavascriptCallback(base::Value(callback_id), base::Value());
+  }
+
   // Send before SendInitialSettings() to allow cloud printer auto select.
   SendCloudPrintEnabled();
-  printer_backend_proxy()->GetDefaultPrinter(base::Bind(
-      &PrintPreviewHandler::SendInitialSettings, weak_factory_.GetWeakPtr()));
+  printer_backend_proxy()->GetDefaultPrinter(
+      base::Bind(&PrintPreviewHandler::SendInitialSettings,
+                 weak_factory_.GetWeakPtr(), callback_id));
 }
 
 void PrintPreviewHandler::HandleForceOpenNewTab(const base::ListValue* args) {
@@ -1228,6 +1236,7 @@ void PrintPreviewHandler::HandleForceOpenNewTab(const base::ListValue* args) {
 }
 
 void PrintPreviewHandler::SendInitialSettings(
+    const std::string& callback_id,
     const std::string& default_printer) {
   base::DictionaryValue initial_settings;
   initial_settings.SetString(kInitiatorTitle,
@@ -1262,8 +1271,7 @@ void PrintPreviewHandler::SendInitialSettings(
 
   if (print_preview_ui()->source_is_modifiable())
     GetNumberFormatAndMeasurementSystem(&initial_settings);
-  web_ui()->CallJavascriptFunctionUnsafe("setInitialSettings",
-                                         initial_settings);
+  ResolveJavascriptCallback(base::Value(callback_id), initial_settings);
 }
 
 void PrintPreviewHandler::ClosePreviewDialog() {