Gallery: do not set zoom more than once in a frame.

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 1852 matching lines @@
    */
   this.lastEvent_ = null;
 
   /**
    * Zoom value just after last touch event.
    * @type {number}
    * @private
    */
   this.lastZoom_ = 1.0;
 
+  /**
+   * @type {number}
+   * @private
+   */
+  this.mouseWheelZoomOperationId_ = 0;
+
   targetElement.addEventListener('touchstart', this.onTouchStart_.bind(this));
   var onTouchEventBound = this.onTouchEvent_.bind(this);
   targetElement.ownerDocument.addEventListener('touchmove', onTouchEventBound);
   targetElement.ownerDocument.addEventListener('touchend', onTouchEventBound);
 
   targetElement.addEventListener('mousedown', this.onMouseDown_.bind(this));
   targetElement.ownerDocument.addEventListener('mousemove',
       this.onMouseMove_.bind(this));
   targetElement.ownerDocument.addEventListener('mouseup',
       this.onMouseUp_.bind(this));
@@ skipping 178 matching lines @@
  */
 TouchHandler.WHEEL_ZOOM_FACTOR = 1.05;
 
 /**
  * Handles mouse wheel events.
  * @param {!Event} event Wheel event.
  * @private
  */
 TouchHandler.prototype.onMouseWheel_ = function(event) {
   var event = assertInstanceof(event, MouseEvent);
-  var viewport = this.slideMode_.getViewport();
   if (!this.enabled_)
     return;
 
   this.stopOperation();
-  this.lastZoom_ = viewport.getZoom();
-  var zoom = this.lastZoom_;
+
+  var viewport = this.slideMode_.getViewport();
+  var zoom = viewport.getZoom();
   if (event.wheelDeltaY > 0) {
     zoom *= TouchHandler.WHEEL_ZOOM_FACTOR;
   } else {
     zoom /= TouchHandler.WHEEL_ZOOM_FACTOR;
   }
-  viewport.setZoom(zoom);
-  this.slideMode_.imageView_.applyViewportChange();
+
+  // Request animation frame not to set zoom more than once in a frame. This is
+  // a fix for https://crbug.com/591033
+  requestAnimationFrame(function(operationId) {
+    if (this.mouseWheelZoomOperationId_ !== operationId)
+      return;
+
+    viewport.setZoom(zoom);
+    this.slideMode_.applyViewportChange();
+  }.bind(this, ++this.mouseWheelZoomOperationId_));
 };
 
 /**
  * Handles mouse down events.
  * @param {!Event} event Wheel event.
  * @private
  */
 TouchHandler.prototype.onMouseDown_ = function(event) {
   var event = assertInstanceof(event, MouseEvent);
   var viewport = this.slideMode_.getViewport();
@@ skipping 24 matching lines @@
 /**
  * Handles mouse up events.
  * @param {!Event} event Wheel event.
  * @private
  */
 TouchHandler.prototype.onMouseUp_ = function(event) {
   if (event.button !== 0)
     return;
   this.clickStarted_ = false;
 };