Specify canvas size by using CSS width/height.

ui/file_manager/gallery/js/image_editor/viewport.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.
 
 'use strict';
 
 /**
  * Viewport class controls the way the image is displayed (scale, offset etc).
  * @constructor
  */
@@ skipping 419 matching lines @@
   this.imageBoundsOnScreenClipped_ = new Rect(
       left, top, right - left, bottom - top);
 };
 
 /**
  * Obtains CSS transformation for the screen image.
  * @return {string} Transformation description.
  */
 Viewport.prototype.getTransformation = function() {
   return 'translate(' + this.offsetX_ + 'px, ' + this.offsetY_ + 'px) ' +
-      'scale(' + (1 / window.devicePixelRatio * this.zoom_) + ')';
+      'scale(' + this.zoom_ + ')';
 };
 
 /**
  * Obtains shift CSS transformation for the screen image.
  * @param {number} dx Amount of shift.
  * @return {string} Transformation description.
  */
 Viewport.prototype.getShiftTransformation = function(dx) {
   return 'translateX(' + dx + 'px) ' + this.getTransformation();
 };
@@ skipping 64 matching lines @@
   var screenWidth = this.screenBounds_.width;
   var screenHeight = this.screenBounds_.height;
   var dx = screenRect.left + screenRect.width / 2 - screenWidth / 2;
   var dy = screenRect.top + screenRect.height / 2 - screenHeight / 2;
   return [
     'translate(' + dx + 'px,' + dy + 'px)',
     'scale(' + scaleX + ',' + scaleY + ')',
     this.getTransformation()
   ].join(' ');
 };