Fix Mosaic view button in the Photo Editor

chrome/browser/resources/file_manager/js/photo/gallery.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.
 
 util.addPageLoadHandler(function() {
   if (!location.hash)
     return;
 
   var pageState;
   if (location.search) {
@@ skipping 226 matching lines @@
       this.onFilenameEditKeydown_.bind(this));
 
   util.createChild(this.toolbar_, 'button-spacer');
 
   this.prompt_ = new ImageEditor.Prompt(
       this.container_, this.displayStringFunction_);
 
   var onThumbnailError = this.context_.onThumbnailError || function() {};
 
   if (this.context_.allowMosaic) {
-    this.modeButton_ = util.createChild(this.toolbar_, 'button mode');
+    this.modeButton_ = util.createChild(this.toolbar_, 'button mode', 'button');
     this.modeButton_.addEventListener('click',
         this.toggleMode_.bind(this, null));
 
     this.mosaicMode_ = new MosaicMode(content,
         this.dataModel_, this.selectionModel_, this.metadataCache_,
         this.toggleMode_.bind(this, null), onThumbnailError);
   }
 
   this.slideMode_ = new SlideMode(this.container_, content,
       this.toolbar_, this.prompt_,
@@ skipping 595 matching lines @@
 Gallery.prototype.updateThumbnails_ = function() {
   if (this.currentMode_ == this.slideMode_)
     this.slideMode_.updateThumbnails();
 
   if (this.mosaicMode_) {
     var mosaic = this.mosaicMode_.getMosaic();
     if (mosaic.isInitialized())
       mosaic.reload();
   }
 };