Gallery.app : shows an error message when it fails to save an image.

ui/file_manager/gallery/js/slide_mode.js

 // Copyright 2014 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.
 
 /**
  * Slide mode displays a single image and has a set of controls to navigate
  * between the images and to edit an image.
  *
  * @param {!HTMLElement} container Main container element.
  * @param {!HTMLElement} content Content container element.
@@ skipping 1245 matching lines @@
  */
 SlideMode.prototype.saveCurrentImage_ = function(item, callback) {
   this.showSpinner_(true);
 
   var savedPromise = this.dataModel_.saveItem(
       this.volumeManager_,
       item,
       this.imageView_.getCanvas(),
       this.shouldOverwriteOriginal_());
 
-  savedPromise.catch(function(error) {
-    // TODO(hirono): Implement write error handling.
-    // Until then pretend that the save succeeded.
-    console.error(error.stack || error);
-  }).then(function() {
+  savedPromise.then(function() {
     this.showSpinner_(false);
     this.flashSavedLabel_();
 
     // Allow changing the 'Overwrite original' setting only if the user
     // used Undo to restore the original image AND it is not a copy.
     // Otherwise lock the setting in its current state.
     var mayChangeOverwrite = !this.editor_.canUndo() && item.isOriginal();
     ImageUtil.setAttribute(this.options_, 'saved', !mayChangeOverwrite);
 
     // Record UMA for the first edit.
     if (this.imageView_.getContentRevision() === 1)
       ImageUtil.metrics.recordUserAction(ImageUtil.getMetricName('Edit'));
 
     callback();
-    cr.dispatchSimpleEvent(this, 'image-saved');
   }.bind(this)).catch(function(error) {
     console.error(error.stack || error);
-  });
+
+    this.showSpinner_(false);
+    this.errorBanner_.show('GALLERY_SAVE_FAILED');
+
+    callback();
+  }.bind(this));
 };
 
 /**
  * Flash 'Saved' label briefly to indicate that the image has been saved.
  * @private
  */
 SlideMode.prototype.flashSavedLabel_ = function() {
   var setLabelHighlighted =
       ImageUtil.setAttribute.bind(null, this.savedLabel_, 'highlighted');
   setTimeout(setLabelHighlighted.bind(null, true), 0);
@@ skipping 563 matching lines @@
   var event = assertInstanceof(event, MouseEvent);
   var viewport = this.slideMode_.getViewport();
   if (!this.enabled_ || !viewport.isZoomed())
     return;
   this.stopOperation();
   viewport.setOffset(
       viewport.getOffsetX() + event.wheelDeltaX,
       viewport.getOffsetY() + event.wheelDeltaY);
   this.slideMode_.applyViewportChange();
 };