Add 2.0 for win/linux as they now supports high dpi

ui/webui/resources/js/util.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.
 
 // <include src="assert.js">
 
 /**
  * Alias for document.getElementById.
  * @param {string} id The ID of the element to find.
  * @return {HTMLElement} The found element or null if not found.
@@ skipping 34 matching lines @@
     // restore
     global[callbackName] = old;
 
     var args = Array.prototype.slice.call(arguments);
     return callback.apply(global, args);
   };
   chrome.send(name, params);
 }
 
 /**
- * Returns the scale factors supported by this platform.
+ * Returns the scale factors supported by this platform for webui
+ * resources.
  * @return {Array} The supported scale factors.
  */
 function getSupportedScaleFactors() {
   var supportedScaleFactors = [];
-  if (cr.isMac || cr.isChromeOS) {
+  if (cr.isMac || cr.isChromeOS || cr.isWindows || cr.isLinux) {
+    // All desktop platforms support zooming which also updates the
+    // renderer's device scale factors (a.k.a devicePixelRatio), and
+    // these platforms has high DPI assets for 2.0x. Use 1x and 2x in
+    // image-set on these platforms so that the renderer can pick the
+    // closest image for the current device scale factor.
     supportedScaleFactors.push(1);
     supportedScaleFactors.push(2);
   } else {
-    // Windows must be restarted to display at a different scale factor.
+    // For other platforms that use fixed device scale factor, use
+    // the window's device pixel ratio.
+    // TODO(oshima): Investigate if Android/iOS need to use image-set.
     supportedScaleFactors.push(window.devicePixelRatio);
   }
   return supportedScaleFactors;
 }
 
 /**
  * Generates a CSS url string.
  * @param {string} s The URL to generate the CSS url for.
  * @return {string} The CSS url string.
  */
@@ skipping 372 matching lines @@
  * @param {number} maxLength The maximum length allowed for the string.
  * @return {string} The original string if its length does not exceed
  *     |maxLength|. Otherwise the first |maxLength| - 1 characters with '...'
  *     appended.
  */
 function elide(original, maxLength) {
   if (original.length <= maxLength)
     return original;
   return original.substring(0, maxLength - 1) + '\u2026';
 }