Print Preview: Make getChildElement return required HTMLElement

chrome/browser/resources/print_preview/settings/copies_settings.js

Index: chrome/browser/resources/print_preview/settings/copies_settings.js
diff --git a/chrome/browser/resources/print_preview/settings/copies_settings.js b/chrome/browser/resources/print_preview/settings/copies_settings.js
index 949c384a1691df9ec35b22d558dd50813f18b53d..369d40058867737bba8bd829a0dd4c8db6749b01 100644
--- a/chrome/browser/resources/print_preview/settings/copies_settings.js
+++ b/chrome/browser/resources/print_preview/settings/copies_settings.js
@@ -85,7 +85,7 @@ cr.define('print_preview', function() {
 
     /** @override */
     enterDocument: function() {
-      this.inputField_ = assert(this.getChildElement('input.user-value'));
+      this.inputField_ = this.getChildElement('input.user-value');
       print_preview.SettingsSection.prototype.enterDocument.call(this);
       this.tracker.add(
           this.inputField_,
@@ -100,7 +100,7 @@ cr.define('print_preview', function() {
           'blur',
           this.onTextfieldBlur_.bind(this));
       this.tracker.add(
-          assert(this.getChildElement('input.collate')),
+          this.getChildElement('input.collate'),
           'click',
           this.onCollateCheckboxClick_.bind(this));
       this.tracker.add(