Gallery: Add animation when zooming pictures.

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 3de743ff6078e545ad48ea50dc225001edf59103..6dec25a0eed57b1d584a86a8c225256423e9da53 100644
--- a/ui/file_manager/gallery/js/slide_mode.js
+++ b/ui/file_manager/gallery/js/slide_mode.js
@@ -869,14 +869,14 @@ SlideMode.prototype.onKeyDown = function(event) {
     case 'Ctrl-U+00BB':  // Ctrl+'=' zoom in.
       if (!this.isEditing()) {
         this.viewport_.setZoomIndex(this.viewport_.getZoomIndex() + 1);
-        this.imageView_.draw();
+        this.imageView_.applyViewportChange();
       }
       break;
 
     case 'Ctrl-U+00BD':  // Ctrl+'-' zoom out.
       if (!this.isEditing()) {
         this.viewport_.setZoomIndex(this.viewport_.getZoomIndex() - 1);
-        this.imageView_.draw();
+        this.imageView_.applyViewportChange();
       }
       break;
   }