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

ui/file_manager/gallery/js/slide_mode.js

Index: ui/file_manager/gallery/js/slide_mode.js
diff --git a/ui/file_manager/gallery/js/slide_mode.js b/ui/file_manager/gallery/js/slide_mode.js
index e5efc167bc3fd2ff463db1e9f63b9b8ff54492e4..f8f7555db00a20049c4a7e1623b9201ff1de2756 100644
--- a/ui/file_manager/gallery/js/slide_mode.js
+++ b/ui/file_manager/gallery/js/slide_mode.js
@@ -1263,11 +1263,7 @@ SlideMode.prototype.saveCurrentImage_ = function(item, callback) {
       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_();
 
@@ -1282,10 +1278,14 @@ SlideMode.prototype.saveCurrentImage_ = function(item, callback) {
       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));
 };
 
 /**