MD Settings: Fix the Network Prediction toggle box.

chrome/browser/resources/settings/controls/settings_boolean_control_behavior.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
  * A behavior to help controls that handle a boolean preference, such as
  * checkbox and toggle button.
  */
 
@@ skipping 37 matching lines @@
     label: {
       type: String,
       value: '',
     },
 
     /** Additional (optional) sub-label. */
     subLabel: {
       type: String,
       value: '',
     },
+
+    /**
+     * For numeric prefs only, the integer value equivalent to the checked
+     * state. This is the value sent to prefs if the user checks the control.
+     */
+    numericCheckedValue: {
+      type: Number,
+      value: 1,
+    },
+
+    /**
+     * For numeric prefs only, the integer value equivalent to the unchecked
+     * state. This is the value sent to prefs if the user unchecks the control.
+     * During initialization, the control is unchecked if and only if the pref
+     * value is equal to the this value. (Values 2, 3, 4, etc. all are checked.)
+     */
+    numericUncheckedValue: {
+      type: Number,
+      value: 0,
+    }

[Dan Beam, 2017/02/09 18:39:10]

can we only add numericUncheckedValue until we need a numericCheckedValue?

also, can we make these vanilla prototype members instead of in properties
(which sets up getters/setters and potentially observers or something)

[tommycli, 2017/02/09 19:19:22]

Done.

But I can't make this a plain prototype member because then this value is
initialized at 0, and then becomes 2 at some point later. This causes havoc with
the pref (sends spurious pref updates).

When it's a property it's initialized at 2. I'm not sure why.

   },
 
   observers: [
     'prefValueChanged_(pref.value)',
   ],
 
   /** Reset the checked state to match the current pref value. */
   resetToPrefValue: function() {
     this.checked = this.getNewValue_(this.pref.value);
   },
 
   /** Update the pref to the current |checked| value. */
   sendPrefChange: function() {
-    /** @type {boolean} */ var newValue = this.getNewValue_(this.checked);
     // Ensure that newValue is the correct type for the pref type, either
     // a boolean or a number.
     if (this.pref.type == chrome.settingsPrivate.PrefType.NUMBER) {
-      this.set('pref.value', newValue ? 1 : 0);
+      this.set('pref.value', this.checked ? this.numericCheckedValue :
+                                            this.numericUncheckedValue);
       return;
     }
-    this.set('pref.value', newValue);
+    this.set('pref.value', this.checked);
   },
 
   /**
    * Polymer observer for pref.value.
    * @param {*} prefValue
    * @private
    */
   prefValueChanged_: function(prefValue) {
     this.checked = this.getNewValue_(prefValue);
   },
 
   /**
    * Polymer observer for checked.
    * @private
    */
   checkedChanged_: function() {
     if (!this.pref || this.noSetPref)
       return;
     this.sendPrefChange();
   },
 
   /**
    * @param {*} value
    * @return {boolean} The value as a boolean, inverted if |inverted| is true.
    * @private
    */
   getNewValue_: function(value) {
+    // For numeric prefs, the control is only false if the value is exactly
+    // equal to the unchecked-equivalent value.
+    if (this.pref.type == chrome.settingsPrivate.PrefType.NUMBER)
+      value = value != this.numericUncheckedValue;
+
     return this.inverted ? !value : !!value;
   },
 
   /**
    * @return {boolean} Whether the checkbox should be disabled.
    * @private
    */
   controlDisabled_: function() {
     return this.disabled || this.isPrefPolicyControlled(assert(this.pref));
   },
 };
 
 /** @polymerBehavior */
 var SettingsBooleanControlBehavior = [
   CrPolicyPrefBehavior,
   PrefControlBehavior,
   SettingsBooleanControlBehaviorImpl,
 ];