Cancel the pending print preview request when the user request to show the system dialog.

chrome/browser/resources/print_preview/print_preview.js

Index: chrome/browser/resources/print_preview/print_preview.js
diff --git a/chrome/browser/resources/print_preview/print_preview.js b/chrome/browser/resources/print_preview/print_preview.js
index 0231ace521274cdd26e63edf2e225b88d8fd9595..38099110c94df0a75bc2787568e8060333c7b1cb 100644
--- a/chrome/browser/resources/print_preview/print_preview.js
+++ b/chrome/browser/resources/print_preview/print_preview.js
@@ -140,6 +140,8 @@ function disableInputElementsInSidebar() {
  * backend to open the native print dialog.
  */
 function onSystemDialogLinkClicked() {
+  if (showingSystemDialog)
+    return;
   showingSystemDialog = true;
   disableInputElementsInSidebar();
   $('system-dialog-throbber').classList.remove('hidden');
@@ -151,6 +153,8 @@ function onSystemDialogLinkClicked() {
  * 'Launch native print dialog' UI.
  */
 function launchNativePrintDialog() {
+  if (showingSystemDialog)
+    return;
   showingSystemDialog = true;
   $('error-button').disabled = true;
   $('native-print-dialog-throbber').classList.remove('hidden');