Material PDF: Adjust behaviour of page selector

chrome/browser/resources/pdf/elements/viewer-page-selector/viewer-page-selector.js

 // Copyright 2015 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.
 
 Polymer({
   is: 'viewer-page-selector',
 
   properties: {
     /**
      * The number of pages the document contains.
      */
     docLength: {
       type: Number,
       value: 1,
       observer: 'docLengthChanged'
     },
 
     /**
-     * The current page being viewed (1-based).
+     * The current page being viewed (1-based). A change to pageNo is mirrored
+     * immediately to the input field. A change to the input field is not
+     * mirrored back until pageNoCommitted() is called and change-page is fired.
      */
     pageNo: {
-      type: String,
-      value: '1'
+      type: Number,
+      value: 1
     },
 
     strings: Object
   },
 
   pageNoCommitted: function() {
-    var page = parseInt(this.pageNo);
-    if (!isNaN(page)) {
+    var page = parseInt(this.$.input.value);
+
+    if (!isNaN(page) && page <= this.docLength && page > 0)
       this.fire('change-page', {page: page - 1});
-      this.$.input.blur();
-    }
+    else
+      this.$.input.value = this.pageNo;
+    this.$.input.blur();
   },
 
   docLengthChanged: function() {
     var numDigits = this.docLength.toString().length;
     this.$.pageselector.style.width = numDigits + 'ch';
     // Set both sides of the slash to the same width, so that the layout is
     // exactly centered.
     this.$['pagelength-spacer'].style.width = numDigits + 'ch';
   },
 
   select: function() {
     this.$.input.select();
   },
 
   /**
    * @return {boolean} True if the selector input field is currently focused.
    */
   isActive: function() {
     return this.shadowRoot.activeElement == this.$.input;
   }
 });