Adding pref to store the user-selected proximity threshold.

chrome/browser/resources/settings/people_page/lock_screen.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-lock-screen' allows the user to change how they unlock their
  * device.
  *
  * Example:
  *
  * <settings-lock-screen
  *   prefs="{{prefs}}">
  * </settings-lock-screen>
  */
 
+/**
+ * Possible values of the proximity threshould displayed to the user.
+ * This should be kept in sync with the enum defined here:
+ * components/proximity_auth/proximity_monitor_impl.cc
+ */
+settings.EasyUnlockProximityThreshold = {
+  VERY_CLOSE: 0,
+  CLOSE: 1,
+  FAR: 2,
+  VERY_FAR: 3,
+};
+
 Polymer({
   is: 'settings-lock-screen',
 
   behaviors: [
     I18nBehavior,
     LockStateBehavior,
     WebUIListenerBehavior,
     settings.RouteObserverBehavior,
   ],
 
@@ skipping 84 matching lines @@
      */
     easyUnlockProximityDetectionAllowed_: {
       type: Boolean,
       value: function() {
         return loadTimeData.getBoolean('easyUnlockAllowed') &&
             loadTimeData.getBoolean('easyUnlockProximityDetectionAllowed');
       },
       readOnly: true,
     },
 
+    /**
+     * Returns the proximity threshold mapping to be displayed in the
+     * threshold selector dropdown menu.

[stevenjb, 2017/07/17 16:43:37]

* @type {DropdownMenuOptionList}

(You will need to include settings_dropdown_menu.js in compiled_resources2.gyp).

[sacomoto, 2017/07/20 19:50:15]

Done.

+     */
+    easyUnlockProximityThresholdMapping_: {
+      type: Array,
+      value: function() {
+        return [
+          {
+            value: settings.EasyUnlockProximityThreshold.VERY_CLOSE,
+            name:
+                loadTimeData.getString('easyUnlockProximityThresholdVeryClose')
+          },
+          {
+            value: settings.EasyUnlockProximityThreshold.CLOSE,
+            name: loadTimeData.getString('easyUnlockProximityThresholdClose')
+          },
+          {
+            value: settings.EasyUnlockProximityThreshold.FAR,
+            name: loadTimeData.getString('easyUnlockProximityThresholdFar')
+          },
+          {
+            value: settings.EasyUnlockProximityThreshold.VERY_FAR,
+            name: loadTimeData.getString('easyUnlockProximityThresholdVeryFar')
+          }
+        ];
+      },
+      readOnly: true,
+    },
+
     /** @private */
     showEasyUnlockTurnOffDialog_: {
       type: Boolean,
       value: false,
     },
 
     /** @private */
     showPasswordPromptDialog_: Boolean,
 
     /** @private */
@@ skipping 201 matching lines @@
   /**
    * @param {boolean} easyUnlockEnabled
    * @param {boolean} proximityDetectionAllowed
    * @private
    */
   getShowEasyUnlockToggle_: function(
       easyUnlockEnabled, proximityDetectionAllowed) {
     return easyUnlockEnabled && proximityDetectionAllowed;
   },
 });