Print Preview: Detecting plugin existence before generating the preview.

chrome/browser/resources/print_preview.js

Index: chrome/browser/resources/print_preview.js
diff --git a/chrome/browser/resources/print_preview.js b/chrome/browser/resources/print_preview.js
index 5c2bb573d08f23304ed4f05c38cf0c3fcf627f2b..84c76984606ecab355c4238574755deebf2f061f 100644
--- a/chrome/browser/resources/print_preview.js
+++ b/chrome/browser/resources/print_preview.js
@@ -48,10 +48,18 @@ const MANAGE_PRINTERS = 'Manage Printers';
  * the printer list.
  */
 function onLoad() {
+  $('system-dialog-link').addEventListener('click', showSystemDialog);
+  $('cancel-button').addEventListener('click', handleCancelButtonClick);
+  $('dummy-viewer').classList.add('hidden');
+
+  if(!checkCompatiblePluginExists()) {
+    displayErrorMessage(localStrings.getString('noPlugin'));
+    return;
+  }
+
   $('printer-list').disabled = true;
   $('print-button').disabled = true;
   $('print-button').addEventListener('click', printFile);
-  $('cancel-button').addEventListener('click', handleCancelButtonClick);
   $('all-pages').addEventListener('click', onPageSelectionMayHaveChanged);
   $('copies').addEventListener('input', copiesFieldChanged);
   $('print-pages').addEventListener('click', handleIndividualPagesCheckbox);
@@ -68,7 +76,6 @@ function onLoad() {
   $('bw').addEventListener('click', function() { setColor(false); });
   $('printer-list').addEventListener(
       'change', updateControlsWithSelectedPrinterCapabilities);
-  $('system-dialog-link').addEventListener('click', showSystemDialog);
   $('increment').addEventListener('click',
                                   function() { onCopiesButtonsClicked(1); });
   $('decrement').addEventListener('click',
@@ -323,7 +330,6 @@ function printFile() {
 function requestPrintPreview() {
   isPreviewStillLoading = true;
   setControlsDisabled(true);
-  $('dancing-dots').classList.remove('hidden');
   $('dancing-dots').classList.remove('invisible');
   chrome.send('getPreview', [getSettingsJSON()]);
 }
@@ -390,6 +396,7 @@ function setColor(color) {
  */
 function displayErrorMessage(errorMessage) {
   isPreviewStillLoading = false;
+  $('dancing-dots').classList.remove('invisible');
   $('dancing-dots-text').classList.add('hidden');
   $('error-text').innerHTML = errorMessage;
   $('error-text').classList.remove('hidden');
@@ -510,6 +517,14 @@ function createPDFPlugin() {
 }
 
 /**
+ * Returns true if a compatible pdf plugin exists, false if it doesn't.
+ */
+function checkCompatiblePluginExists() {
+  var dummyPlugin = $('dummy-viewer')
+  return !!dummyPlugin.onload;
+}
+
+/**
  * Updates the state of print button depending on the user selection.
  * The button is enabled only when the following conditions are true.
  * 1) The selected page ranges are valid.