Print Preview: Associating preview requests and responses using an identifier

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 bf0e573411fb4c7e9c97e1770e30397b080262f4..6b903a24e10c00a634028cd82055656744b6479a 100644
--- a/chrome/browser/resources/print_preview/print_preview.js
+++ b/chrome/browser/resources/print_preview/print_preview.js
@@ -23,6 +23,9 @@ var defaultOrLastUsedPrinterName = '';
 // True when a pending print preview request exists.
 var hasPendingPreviewRequest = false;
 
+// The ID of the last preview request.
+var lastPreviewRequestID = -1;
+
 // True when a pending print file request exists.
 var hasPendingPrintFileRequest = false;
 
@@ -257,15 +260,15 @@ function getDuplexMode() {
 }
 
 /**
- * Creates a JSON string based on the values in the printer settings.
+ * Creates an object based on the values in the printer settings.
  *
- * @return {string} JSON string with print job settings.
+ * @return {Object} Object containing print job settings.
  */
-function getSettingsJSON() {
+function getSettings() {
   var deviceName = getSelectedPrinterName();
   var printToPDF = (deviceName == PRINT_TO_PDF);
 
-  return JSON.stringify(
+  var settings =
       {'deviceName': deviceName,
        'pageRange': pageSettings.selectedPageRanges,
        'printAll': pageSettings.allPagesRadioButton.checked,
@@ -274,7 +277,16 @@ function getSettingsJSON() {
        'collate': isCollated(),
        'landscape': isLandscape(),
        'color': isColor(),
-       'printToPDF': printToPDF});
+       'printToPDF': printToPDF,
+       'requestID': 0};
+  return settings;
+}
+
+/**
+ * @return {number} The next unused preview request id.
+ */
+function generatePreviewRequestID() {
+  return ++lastPreviewRequestID;
 }
 
 /**
@@ -345,7 +357,7 @@ function cancelPendingPrintRequest() {
  * Sends a message to initiate print workflow.
  */
 function sendPrintFileRequest() {
-  chrome.send('print', [getSettingsJSON()]);
+  chrome.send('print', [JSON.stringify(getSettings())]);
 }
 
 /**
@@ -358,7 +370,9 @@ function requestPrintPreview() {
   if (!isTabHidden)
     showLoadingAnimation();
 
-  chrome.send('getPreview', [getSettingsJSON()]);
+  var settings = getSettings();
+  settings.requestID = generatePreviewRequestID();
+  chrome.send('getPreview', [JSON.stringify(settings)]);
 }
 
 /**
@@ -545,8 +559,15 @@ function onDidPreviewPage(pageNumber) {
  * @param {string} jobTitle The print job title.
  * @param {boolean} modifiable If the preview is modifiable.
  * @param {string} previewUid Preview unique identifier.
- */
-function updatePrintPreview(jobTitle, modifiable, previewUid) {
+ * @param {string} previewRequestId The preview request id that resulted in this
+ *     response.
+ */
+function updatePrintPreview(jobTitle,
+                            modifiable,
+                            previewUid,
+                            previewRequestId) {
+  if (lastPreviewRequestID != previewRequestId)
+    return;
   hasPendingPreviewRequest = false;
 
   if (checkIfSettingsChangedAndRegeneratePreview())