Launch mosaic view only if most of the selected files are images.

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 317 matching lines @@
   return button;
 };
 
 /**
  * Load the content.
  *
  * @param {Array.<string>} urls Array of urls.
  * @param {Array.<string>} selectedUrls Array of selected urls.
  */
 Gallery.prototype.load = function(urls, selectedUrls) {
-  if (!this.mosaicMode_ && selectedUrls.length > 1) {
-    // If the mosaic is disabled revert to the old multiple selection behavior.
-    urls = selectedUrls;  // Only show the items selected in the file list.
-    selectedUrls = selectedUrls.slice(0, 1);  // Force single selection.
-  }
-
   var items = [];
   for (var index = 0; index < urls.length; ++index) {
     items.push(new Gallery.Item(urls[index]));
   }
   this.dataModel_.push.apply(this.dataModel_, items);
 
   this.selectionModel_.adjustLength(this.dataModel_.length);
 
   for (var i = 0; i != selectedUrls.length; i++) {
     var selectedIndex = urls.indexOf(selectedUrls[i]);
     if (selectedIndex >= 0)
       this.selectionModel_.setIndexSelected(selectedIndex, true);
     else
       console.error('Cannot select ' + selectedUrls[i]);
   }
 
   if (this.selectionModel_.selectedIndexes.length == 0)
     this.onSelection_();
 
   var mosaic = this.mosaicMode_ && this.mosaicMode_.getMosaic();
-  if (mosaic &&
-      (selectedUrls.length != 1 ||
-      (this.context_.pageState &&
-          this.context_.pageState.gallery == 'mosaic'))) {
+
+  // Mosaic view should show up if most of the selected files are images.
+  var imagesCount = 0;
+  for (var i = 0; i != selectedUrls.length; i++) {
+    if (FileType.getMediaType(selectedUrls[i]) == 'image')
+      imagesCount++;
+  }
+  var mostlyImages = imagesCount > (selectedUrls.length / 2.0);
+
+  var forcedMosaic = (this.context_.pageState &&
+       this.context_.pageState.gallery == 'mosaic');
+
+  var showMosaic = (mostlyImages && selectedUrls.length > 1) || forcedMosaic;
+  if (mosaic && showMosaic) {
     this.setCurrentMode_(this.mosaicMode_);
     mosaic.init();
     mosaic.show();
     this.inactivityWatcher_.check();  // Show the toolbar.
     cr.dispatchSimpleEvent(this, 'loaded');
   } else {
     this.setCurrentMode_(this.slideMode_);
     var maybeLoadMosaic = function() {
       if (mosaic)
         mosaic.init();
@@ skipping 517 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();
   }
 };