cros: Use runtime stylus detection for ash palette.

chrome/browser/resources/settings/device_page/device_page.js

Index: chrome/browser/resources/settings/device_page/device_page.js
diff --git a/chrome/browser/resources/settings/device_page/device_page.js b/chrome/browser/resources/settings/device_page/device_page.js
index b3bb4acc65d12446faed1485211b399f86723921..0dd856b8b96b5cf42b2a8ed6e627a47b4d96d82f 100644
--- a/chrome/browser/resources/settings/device_page/device_page.js
+++ b/chrome/browser/resources/settings/device_page/device_page.js
@@ -22,8 +22,8 @@ Polymer({
     },
 
     /**
-     * |hasMouse_| and |hasTouchpad_| start undefined so observers don't trigger
-     * until both have been populated.
+     * |hasMouse_|, |hasTouchpad_|, and |hasStylus_| start undefined so
+     * observers don't trigger until they have been populated.
      * @private
      */
     hasMouse_: Boolean,
@@ -32,13 +32,7 @@ Polymer({
     hasTouchpad_: Boolean,
 
     /** @private */
-    stylusAllowed_: {
-      type: Boolean,
-      value: function() {
-        return loadTimeData.getBoolean('stylusAllowed');
-      },
-      readOnly: true,
-    },
+    hasStylus_: Boolean,

[stevenjb, 2017/02/03 23:11:26]

This should actually initialize to 'false', otherwise it will be undefined which
can have unexpected behavior (see https://github.com/Polymer/polymer/issues/2447
if you are curious). I believe that currently this will behave as expected, but
better I think to explicitly hide the section initially.

[jdufault, 2017/02/06 21:44:41]

Done; I was following the pattern for hasMouse_ and hasTouchpad_ so I've updated
those so they also explicitly initialize to false.

 
     /**
      * Whether power status and settings should be fetched and displayed.
@@ -109,6 +103,10 @@ Polymer({
         'has-touchpad-changed', this.set.bind(this, 'hasTouchpad_'));
     settings.DevicePageBrowserProxyImpl.getInstance().initializePointers();
 
+    this.addWebUIListener(
+        'has-stylus-changed', this.set.bind(this, 'hasStylus_'));
+    settings.DevicePageBrowserProxyImpl.getInstance().initializeStylus();
+
     if (this.enablePowerSettings_) {
       this.addWebUIListener(
           'battery-status-changed', this.set.bind(this, 'batteryStatus_'));