Material PDF: Style audit and cleanup

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.
 
-var DIGIT_LENGTH = 0.6;
-
 Polymer({
   is: 'viewer-page-selector',
 
   properties: {
     /**
      * The number of pages the document contains.
      */
     docLength: {
       type: Number,
       value: 1,
@@ skipping 12 matching lines @@
   pageNoCommitted: function() {
     var page = parseInt(this.pageNo);
     if (!isNaN(page)) {
       this.fire('change-page', {page: page - 1});
       this.$.input.blur();
     }
   },
 
   docLengthChanged: function() {
     var numDigits = this.docLength.toString().length;
-    this.$.pageselector.style.width = (numDigits * DIGIT_LENGTH) + 'em';
+    this.$.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;
   }
 });