Add scale to settings-slider

chrome/browser/resources/settings/controls/settings_slider.js

 // Copyright 2016 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.
 
 /**
  * @fileoverview
  * settings-slider wraps a paper-slider. It maps the slider's values from a
  * linear UI range to a range of real values.  When |value| does not map exactly
  * to a tick mark, it interpolates to the nearest tick.
  *
  * Unlike paper-slider, there is no distinction between value and
  * immediateValue; when either changes, the |value| property is updated.
  */
 Polymer({
   is: 'settings-slider',
 
   behaviors: [CrPolicyPrefBehavior],
 
   properties: {
     /** @type {!chrome.settingsPrivate.PrefObject} */
     pref: Object,
 
     /** @type {!Array<number>} Values corresponding to each tick. */
     tickValues: {type: Array, value: []},
 
+    /**
+     * A scale factor used to support fractional pref values since paper-slider
+     * only supports integers. This is not compatible with |tickValues|,
+     * i.e. if |scale| is not 1 then |tickValues| must be empty.
+     */
+    scale: {
+      type: Number,
+      value: 1,
+    },
+
     min: Number,
 
     max: Number,
 
     labelMin: String,
 
     labelMax: String,
 
     disabled: Boolean,
 
@@ skipping 15 matching lines @@
    */
   onSliderChanged_: function() {
     var sliderValue = isNaN(this.$.slider.immediateValue)
                          ? this.$.slider.value
                          : this.$.slider.immediateValue;
 
     var newValue;
     if (this.tickValues && this.tickValues.length > 0)
       newValue = this.tickValues[sliderValue];
     else
-      newValue = sliderValue;
+      newValue = sliderValue / this.scale;
 
     this.set('pref.value', newValue);
   },
 
   /** @private */
   computeDisableSlider_: function() {
     return this.disabled || this.isPrefEnforced();
   },
 
   /**
    * Updates the knob position when |pref.value| changes. If the knob is still
    * being dragged, this instead forces |pref.value| back to the current
    * position.
    * @private
    */
   valueChanged_: function() {
     // If |tickValues| is empty, simply set current value to the slider.
     if (this.tickValues.length == 0) {
-      this.$.slider.value = this.pref.value;
+      this.$.slider.value =
+          /** @type {number} */ (this.pref.value) * this.scale;
       return;
     }
+    assert(this.scale == 1);
 
     // First update the slider settings if |tickValues| was set.
     var numTicks = Math.max(1, this.tickValues.length);
     this.$.slider.max = numTicks - 1;
     // Limit the number of ticks to 10 to keep the slider from looking too busy.
     /** @const */ var MAX_TICKS = 10;
     this.$.slider.snaps = numTicks < MAX_TICKS;
     this.$.slider.maxMarkers = numTicks < MAX_TICKS ? numTicks : 0;
 
     if (this.$.slider.dragging && this.tickValues.length > 0 &&
@@ skipping 37 matching lines @@
       if (difference < minDifference) {
         closestIndex = i;
         minDifference = difference;
       }
     }
 
     assert(typeof closestIndex != 'undefined');
     return closestIndex;
   },
 });