Reset only invalid custom margins.

chrome/browser/resources/print_preview/data/print_ticket_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';
 
   // TODO(rltoscano): Maybe clear print ticket when destination changes. Or
   // better yet, carry over any print ticket state that is possible. I.e. if
   // destination changes, the new destination might not support duplex anymore,
@@ skipping 405 matching lines @@
      */
     onSelectedDestinationCapabilitiesReady_: function() {
       var caps = this.destinationStore_.selectedDestination.capabilities;
       var isFirstUpdate = this.capabilitiesHolder_.get() == null;
       this.capabilitiesHolder_.set(caps);
       if (isFirstUpdate) {
         this.isInitialized_ = true;
         cr.dispatchSimpleEvent(this, PrintTicketStore.EventType.INITIALIZE);
       } else {
         // Reset user selection for certain ticket items.
-        this.customMargins_.updateValue(null);
-
         if (this.marginsType_.getValue() ==
-            print_preview.ticket_items.MarginsType.Value.CUSTOM) {
+            print_preview.ticket_items.MarginsType.Value.CUSTOM &&
+            !this.customMargins_.wouldValueBeValid(
+                 this.customMargins_.getValue())) {
+          this.customMargins_.updateValue(null);
           this.marginsType_.updateValue(
               print_preview.ticket_items.MarginsType.Value.DEFAULT);
         }
         cr.dispatchSimpleEvent(
             this, PrintTicketStore.EventType.CAPABILITIES_CHANGE);
       }
     },
 
     /**
      * Called when document data model has changed. Dispatches a print ticket
      * store event.
      * @private
      */
     onDocumentInfoChange_: function() {
       cr.dispatchSimpleEvent(this, PrintTicketStore.EventType.DOCUMENT_CHANGE);
     },
   };
 
   // Export
   return {
     PrintTicketStore: PrintTicketStore
   };
 });