MD Settings: Bluetooth: Clean up observers and discovery logic

chrome/browser/resources/settings/bluetooth_page/bluetooth_subpage.js

 // Copyright 2017 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-bluetooth-subpage' is the settings subpage for managing bluetooth
  *  properties and devices.
  */
 
 // NOTE(dbeam): even though this behavior is only used privately, it must
 // be globally accessible for Closure's --polymer_pass to compile happily.
 
 Polymer({
   is: 'settings-bluetooth-subpage',
 
   behaviors: [
     I18nBehavior,
     CrScrollableBehavior,
     settings.RouteObserverBehavior,
   ],
 
   properties: {
     /** Reflects the bluetooth-page property. */
     bluetoothEnabled: {
       type: Boolean,
-      observer: 'bluetoothEnabledChanged_',
       notify: true,
     },
 
     /**
      * The bluetooth adapter state, cached by bluetooth-page.
      * @type {!chrome.bluetooth.AdapterState|undefined}
      */
     adapterState: Object,
 
     /** Informs bluetooth-page whether to show the spinner in the header. */
@@ skipping 103 matching lines @@
     },
   },
 
   observers: [
     'adapterStateChanged_(adapterState.*)',
     'deviceListChanged_(deviceList_.*)',
   ],
 
   /**
    * Listener for chrome.bluetooth.onBluetoothDeviceAdded/Changed events.
-   * @type {function(!chrome.bluetooth.Device)|undefined}
+   * @type {?function(!chrome.bluetooth.Device)}
    * @private
    */
-  bluetoothDeviceUpdatedListener_: undefined,
+  bluetoothDeviceUpdatedListener_: null,
 
   /**
    * Listener for chrome.bluetooth.onBluetoothDeviceRemoved events.
-   * @type {function(!chrome.bluetooth.Device)|undefined}
+   * @type {?function(!chrome.bluetooth.Device)}
    * @private
    */
-  bluetoothDeviceRemovedListener_: undefined,
+  bluetoothDeviceRemovedListener_: null,
 
   /** @override */
   attached: function() {
     this.bluetoothDeviceUpdatedListener_ =
+        this.bluetoothDeviceUpdatedListener_ ||
         this.onBluetoothDeviceUpdated_.bind(this);
     this.bluetooth.onDeviceAdded.addListener(
         this.bluetoothDeviceUpdatedListener_);
     this.bluetooth.onDeviceChanged.addListener(
         this.bluetoothDeviceUpdatedListener_);
 
     this.bluetoothDeviceRemovedListener_ =
+        this.bluetoothDeviceRemovedListener_ ||
         this.onBluetoothDeviceRemoved_.bind(this);
     this.bluetooth.onDeviceRemoved.addListener(
         this.bluetoothDeviceRemovedListener_);
   },
 
   /** @override */
   detached: function() {
-    if (this.bluetoothAdapterStateChangedListener_) {
-      this.bluetooth.onAdapterStateChanged.removeListener(
-          this.bluetoothAdapterStateChangedListener_);
-    }
-    if (this.bluetoothDeviceUpdatedListener_) {
-      this.bluetooth.onDeviceAdded.removeListener(
-          this.bluetoothDeviceUpdatedListener_);
-      this.bluetooth.onDeviceChanged.removeListener(
-          this.bluetoothDeviceUpdatedListener_);
-    }
+    this.bluetooth.onDeviceAdded.removeListener(
+        assert(this.bluetoothDeviceUpdatedListener_));
+    this.bluetooth.onDeviceChanged.removeListener(
+        assert(this.bluetoothDeviceUpdatedListener_));
+    this.bluetooth.onDeviceRemoved.removeListener(
+        assert(this.bluetoothDeviceRemovedListener_));
   },
 
   /**
    * settings.RouteObserverBehavior
    * @param {!settings.Route} route
    * @protected
    */
   currentRouteChanged: function(route) {
-    if (route == settings.Route.BLUETOOTH_DEVICES) {
-      if (this.bluetoothEnabled)
-        this.startDiscovery_();
-    } else {
-      this.stopDiscovery_();
-    }
+    this.updateDiscovery_();
   },
 
   /** @private */
   computeShowSpinner_: function() {
     return !this.dialogId_ && this.get('adapterState.discovering');
   },
 
   /** @private */
   adapterStateChanged_: function() {
+    this.updateDiscovery_();
     this.updateDeviceList_();
   },
 
   /** @private */
-  bluetoothEnabledChanged_: function() {
-    if (settings.getCurrentRoute() == settings.Route.BLUETOOTH_DEVICES &&
-        this.bluetoothEnabled) {
-      this.startDiscovery_();
-    } else {
-      this.stopDiscovery_();
-    }
-  },
-
-  /** @private */
   deviceListChanged_: function() {
     this.saveScroll(this.$.pairedDevices);
     this.saveScroll(this.$.unpairedDevices);
     this.pairedDeviceList_ = this.deviceList_.filter(function(device) {
       return !!device.paired || !!device.connecting;
     });
     this.unpairedDeviceList_ = this.deviceList_.filter(function(device) {
       return !device.paired;
     });
     this.updateScrollableContents();
     this.restoreScroll(this.$.unpairedDevices);
     this.restoreScroll(this.$.pairedDevices);
   },
 
   /** @private */
   selectedPairedItemChanged_: function() {
     if (this.selectedPairedItem_)
       this.connectDevice_(this.selectedPairedItem_);
   },
 
   /** @private */
   selectedUnpairedItemChanged_: function() {
     if (this.selectedUnpairedItem_)
       this.connectDevice_(this.selectedUnpairedItem_);
   },
 
+  /** @private */
+  updateDiscovery_: function() {
+    if (!this.adapterState || !this.adapterState.powered)
+      return;
+    if (settings.getCurrentRoute() == settings.Route.BLUETOOTH_DEVICES)
+      this.startDiscovery_();
+    else
+      this.stopDiscovery_();
+  },
+
   /**
    * If bluetooth is enabled, request the complete list of devices and update
    * this.deviceList_.
    * @private
    */
   updateDeviceList_: function() {
     if (!this.bluetoothEnabled) {
       this.deviceList_ = [];
       return;
     }
@@ skipping 204 matching lines @@
     Polymer.dom.flush();
     this.$.deviceDialog.open();
   },
 
   /** @private */
   onDialogClosed_: function() {
     this.dialogId_ = '';
     this.pairingDevice_ = undefined;
   },
 });