Fix CrOS reverting to Save as PDF and random PDF preview fail

chrome/browser/resources/print_preview/data/destination_store.js

 // 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.
 
 cr.define('print_preview', function() {
   'use strict';
 
   /**
    * A data store that stores destinations and dispatches events when the data
    * store changes.
@@ skipping 651 matching lines @@
      *     default destination selection rules.
      */
     init: function(
         isInAppKioskMode,
         systemDefaultDestinationId,
         serializedDefaultDestinationSelectionRulesStr) {
       this.pdfPrinterEnabled_ = !isInAppKioskMode;
       this.systemDefaultDestinationId_ = systemDefaultDestinationId;
       this.createLocalPdfPrintDestination_();
 
-      if (!this.appState_.selectedDestinationId ||
-          !this.appState_.selectedDestinationOrigin) {
+      if (!this.appState_.selectedDestination ||
+          !this.appState_.selectedDestination.id ||
+          !this.appState_.selectedDestination.origin) {
         var destinationMatch = this.convertToDestinationMatch_(
             serializedDefaultDestinationSelectionRulesStr);
         if (destinationMatch) {
           this.fetchMatchingDestination_(destinationMatch);
           return;
         }
       }
 
       if (!this.systemDefaultDestinationId_ &&
-          !(this.appState_.selectedDestinationId &&
-            this.appState_.selectedDestinationOrigin)) {
+          (!this.appState_.selectedDestination ||
+           !this.appState_.selectedDestination.id ||
+           !this.appState_.selectedDestination.origin)) {
         this.selectPdfDestination_();
         return;
       }
 
       var origin = print_preview.Destination.Origin.LOCAL;
       var id = this.systemDefaultDestinationId_;
       var account = '';
       var name = '';
       var capabilities = null;
       var extensionId = '';
       var extensionName = '';
       var foundDestination = false;
       if (this.appState_.recentDestinations) {
-        // Run through the destinations backwards the most recently used is set
-        // as the initially selected destination.
-        for (var i = this.appState_.recentDestinations.length - 1; i >= 0;
-             i--) {
+        // Run through the destinations forward. As soon as we find a
+        // destination, don't select any future destinations, just mark
+        // them recent. Otherwise, there is a race condition between selecting
+        // destinations/updating the print ticket and this selecting a new
+        // destination that causes random print preview errors.
+        for (var i = 0; i < this.appState_.recentDestinations.length; i++) {
           origin = this.appState_.recentDestinations[i].origin;
           id = this.appState_.recentDestinations[i].id;
           account = this.appState_.recentDestinations[i].account || '';
           name = this.appState_.recentDestinations[i].name || '';
           capabilities = this.appState_.recentDestinations[i].capabilities;
           extensionId = this.appState_.recentDestinations[i].extensionId ||
                         '';
           extensionName =
               this.appState_.recentDestinations[i].extensionName || '';
           var candidate =
               this.destinationMap_[this.getDestinationKey_(origin,
                                                            id, account)];
           if (candidate != null) {
-            this.selectDestination(candidate);
+            if (!foundDestination)
+              this.selectDestination(candidate);
             candidate.isRecent = true;
             foundDestination = true;
-          } else {
+          } else if (!foundDestination) {
             foundDestination = this.fetchPreselectedDestination_(
                                     origin,
                                     id,
                                     account,
                                     name,
                                     capabilities,
                                     extensionId,
                                     extensionName);
           }
         }
@@ skipping 197 matching lines @@
           displayNameRegExp,
           true /*skipVirtualDestinations*/);
     },
 
     /**
      * @return {print_preview.DestinationMatch} Creates rules matching
      *     previously selected destination.
      * @private
      */
     convertPreselectedToDestinationMatch_: function() {
-      if (this.appState_.selectedDestinationId &&
-          this.appState_.selectedDestinationOrigin) {
+      if (this.appState_.selectedDestination &&

[dpapad, 2016/11/19 01:37:58]

Can you package these three checks in a helper and re-use? They are currently
repeated in 3 places in this file (lines 672-674,  684-686, and here).

[rbpotter, 2016/11/19 02:44:58]

Done.

+          this.appState_.selectedDestination.id &&
+          this.appState_.selectedDestination.origin) {
         return this.createExactDestinationMatch_(
-            this.appState_.selectedDestinationOrigin,
-            this.appState_.selectedDestinationId);
+            this.appState_.selectedDestination.origin,
+            this.appState_.selectedDestination.id);
       }
       if (this.systemDefaultDestinationId_) {
         return this.createExactDestinationMatch_(
             print_preview.Destination.Origin.LOCAL,
             this.systemDefaultDestinationId_);
       }
       return null;
     },
 
     /**
@@ skipping 380 matching lines @@
           destination.capabilities_);
       destination.capabilities_ = DestinationStore.sortMediaSizes_(
           destination.capabilities_);
       var existingDestination = this.destinationMap_[this.getKey_(destination)];
       if (existingDestination != null) {
         existingDestination.capabilities = destination.capabilities;
       } else {
         this.insertDestination_(destination);
       }
 
-      if (existingDestination == this.selectedDestination_ ||
-          destination == this.selectedDestination_) {
+      if (this.selectedDestination_ &&
+          (existingDestination == this.selectedDestination_ ||
+           destination == this.selectedDestination_)) {
         this.appState_.persistSelectedDestination(this.selectedDestination_);
         cr.dispatchSimpleEvent(
             this,
             DestinationStore.EventType.SELECTED_DESTINATION_CAPABILITIES_READY);
       }
     },
 
     /**
      * Called when the search for Privet printers is done.
      * @private
@@ skipping 385 matching lines @@
       return this.getDestinationKey_(
           destination.origin, destination.id, destination.account);
     }
   };
 
   // Export
   return {
     DestinationStore: DestinationStore
   };
 });