Fixed multiple undo in the Files.app's image editor.

chrome/browser/resources/file_manager/js/image_editor/commands.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.
 
 /**
  * Command queue is the only way to modify images.
  * Supports undo/redo.
  * Command execution is asynchronous (callback-based).
  *
  * @param {Document} document Document to create canvases in.
  * @param {HTMLCanvasElement} canvas The canvas with the original image.
  * @param {function(callback)} saveFunction Function to save the image.
  * @constructor
  */
 function CommandQueue(document, canvas, saveFunction) {
   this.document_ = document;
   this.undo_ = [];
   this.redo_ = [];
   this.subscribers_ = [];
 
-  this.baselineImage_ = canvas;
   this.currentImage_ = canvas;
+
+  this.baselineImage_ = document.createElement('canvas');
+  this.baselineImage_.width = this.currentImage_.width;
+  this.baselineImage_.height = this.currentImage_.height;
+  var context = this.baselineImage_.getContext('2d');
+  context.drawImage(this.currentImage_, 0, 0);
+
   this.previousImage_ = document.createElement('canvas');
+  this.previousImageAvailable_ = false;
 
   this.saveFunction_ = saveFunction;
 
   this.busy_ = false;
 
   this.UIContext_ = {};
 }
 
 /**
  * Attach the UI elements to the command queue.
@@ skipping 81 matching lines @@
  * @param {function} callback Completion callback.
  * @private
  */
 CommandQueue.prototype.doExecute_ = function(command, uiContext, callback) {
   if (!this.currentImage_)
     throw new Error('Cannot operate on null image');
 
   // Remember one previous image so that the first undo is as fast as possible.
   this.previousImage_.width = this.currentImage_.width;
   this.previousImage_.height = this.currentImage_.height;
+  this.previousImageAvailable_ = true;
   var context = this.previousImage_.getContext('2d');
   context.drawImage(this.currentImage_, 0, 0);
 
   command.execute(
       this.document_,
       this.currentImage_,
       function(result, opt_delay) {
         this.currentImage_ = result;
         callback(opt_delay);
       }.bind(this),
@@ skipping 37 matching lines @@
   this.redo_.push(command);
 
   var self = this;
 
   function complete() {
     var delay = command.revertView(
         self.currentImage_, self.UIContext_.imageView);
     self.commit_(delay);
   }
 
-  if (this.previousImage_) {
+  if (this.previousImageAvailable_) {
     // First undo after an execute call.
     this.currentImage_.width = this.previousImage_.width;
     this.currentImage_.height = this.previousImage_.height;
     var context = this.currentImage_.getContext('2d');
     context.drawImage(this.previousImage_, 0, 0);
 
     // Free memory.
     this.previousImage_.width = 0;
     this.previousImage_.height = 0;
+    this.previousImageAvailable_ = false;
 
     complete();
     // TODO(kaznacheev) Consider recalculating previousImage_ right here
     // by replaying the commands in the background.
   } else {
-    this.currentImage_ = this.baselineImage_;
+    this.currentImage_.width = this.baselineImage_.width;
+    this.currentImage_.height = this.baselineImage_.height;
+    var context = this.currentImage_.getContext('2d');
+    context.drawImage(this.baselineImage_, 0, 0);
 
     var replay = function(index) {
       if (index < self.undo_.length)
         self.doExecute_(self.undo_[index], {}, replay.bind(null, index + 1));
       else {
         complete();
       }
     };
 
     replay(0);
@@ skipping 18 matching lines @@
 };
 
 /**
  * Closes internal buffers. Call to ensure, that internal buffers are freed
  * as soon as possible.
  */
 CommandQueue.prototype.close = function() {
   // Free memory used by the undo buffer.
   this.previousImage_.width = 0;
   this.previousImage_.height = 0;
+  this.previousImageAvailable_ = false;
+
+  this.baselineImage_.width = 0;
+  this.baselineImage_.height = 0;
 };
 
 /**
  * Command object encapsulates an operation on an image and a way to visualize
  * its result.
  *
  * @param {string} name Command name.
  * @constructor
  */
 function Command(name) {
@@ skipping 175 matching lines @@
 
   function onProgressInvisible(updatedRow, rowCount) {
     if (updatedRow == rowCount) {
       callback(result);
     }
   }
 
   filter.applyByStrips(result, srcCanvas, this.filter_,
       uiContext.imageView ? onProgressVisible : onProgressInvisible);
 };