Check the actual size of canvas to update.

Previously the gallery checks the sequence number to find out whether the update
for canvas size is needed or not.  The sequence number is incremented when
variables that affect canvas size are updated. But sometimes, the
canvas size goes to be out of sync.

BUG=245926
TEST=manually

Review URL: https://codereview.chromium.org/399383002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284052 0039d316-1c4b-4281-b951-d872f2087c98

ui/file_manager/gallery/js/image_editor/image_view.js

@@ -20,7 +20,6 @@ function ImageView(container, viewport) {
   this.document_ = container.ownerDocument;
   this.contentGeneration_ = 0;
   this.displayedContentGeneration_ = 0;
-  this.displayedViewportGeneration_ = 0;
 
   this.imageLoader_ = new ImageUtil.ImageLoader(this.document_);
   // We have a separate image loader for prefetch which does not get cancelled
@@ -104,20 +103,16 @@ ImageView.prototype.draw = function() {
     return;
 
   var forceRepaint = false;
-
-  if (this.displayedViewportGeneration_ !==
-      this.viewport_.getCacheGeneration()) {
-    this.displayedViewportGeneration_ = this.viewport_.getCacheGeneration();
-
+  var deviceBounds = this.viewport_.getDeviceBounds();
+  if (deviceBounds.width != this.screenImage_.width ||
+      deviceBounds.height != this.screenImage_.height) {
     this.setupDeviceBuffer(this.screenImage_);
-
     forceRepaint = true;
   }
 
   if (forceRepaint ||
       this.displayedContentGeneration_ !== this.contentGeneration_) {
     this.displayedContentGeneration_ = this.contentGeneration_;
-
     ImageUtil.trace.resetTimer('paint');
     this.paintDeviceRect(this.contentCanvas_, new Rect(this.contentCanvas_));
     ImageUtil.trace.reportTimer('paint');
@@ -184,16 +179,9 @@ ImageView.prototype.getContentRevision = function() {
  * @param {Rect} imageRect Rectangle region of the canvas to be rendered.
  */
 ImageView.prototype.paintDeviceRect = function(canvas, imageRect) {
-  // Check canvas size.
-  var deviceBounds = this.viewport_.getDeviceBounds();
-  if (this.screenImage_.width != deviceBounds.width ||
-      this.screenImage_.height != deviceBounds.height) {
-    console.error('The size of canvas is invalid.', (new Error).stack);
-    return;
-  }
-
   // Map the rectangle in full resolution image to the rectangle in the device
   // canvas.
+  var deviceBounds = this.viewport_.getDeviceBounds();
   var scaleX = deviceBounds.width / canvas.width;
   var scaleY = deviceBounds.height / canvas.height;
   var deviceRect = new Rect(