Reset only invalid custom margins.

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

Index: chrome/browser/resources/print_preview/data/print_ticket_store.js
diff --git a/chrome/browser/resources/print_preview/data/print_ticket_store.js b/chrome/browser/resources/print_preview/data/print_ticket_store.js
index 9ca5a8ac88b1d0fd115df459c8131cd553f84cd8..963ee20683a7a67d371b3d8b51c9b3013b70cbcd 100644
--- a/chrome/browser/resources/print_preview/data/print_ticket_store.js
+++ b/chrome/browser/resources/print_preview/data/print_ticket_store.js
@@ -423,10 +423,11 @@ cr.define('print_preview', function() {
         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);
         }