md-settings: Added settings for fingerprint unlock.

chrome/browser/resources/settings/people_page/fingerprint_list.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.
+
+(function() {
+'use strict';
+
+/**
+ * The max number of fingerprints this list can hold.
+ * @const {number}
+ */
+var MAX_NUMBER_FINGERPRINTS_ALLOWED = 5;
+
+Polymer({
+  is: 'settings-fingerprint-list',
+
+  behaviors: [
+    I18nBehavior,
+  ],
+
+  properties: {
+    /**
+     * The list of fingerprint objects.
+     * @private {!Array<string>}
+     */
+    fingerprints_: {
+      type: Array,
+      value: function() {
+        return [];
+      }
+    }
+  },
+
+  /**
+   * Adds a fingerprint with a default name.
+   * @private
+   */
+  onAddFingerprint_: function() {
+    // Determines what the newly added fingerprint's name should be.
+    // TODO(sammiequon): Add fingerprint using private API once it is ready.
+
+    var fingerprintName;
+    for (var i = 1; i <= MAX_NUMBER_FINGERPRINTS_ALLOWED; ++i) {

[Dan Beam, 2017/01/27 23:11:07]

i still think this loop is confusing.

if i reach i>=MAX_NUMBER_FINGERPRINTS_ALLOWED, do I still want to push
fingerprintName into this.fingerprints_?  can you restructure the code so it's
clearer this isn't a potential programming error?

maybe:

for (var i = 1; i <= MAX_NUMBER_FINGERPRINTS_ALLOWED; ++i) {
  var fingerprintName = this.i18n('lockScreenFingerprintNewName', i);
  if (!this.fingerprints_.includes(fingerprintName)) {
    this.push('fingerprints_', fingerprintName);
    break;
  }
}

[sammiequon, 2017/01/27 23:37:37]

i should never > MAX_NUMBER_FINGERPRINTS_ALLOWED since this event cannot be
fired when fingerprints_ has MAX_NUMBER_FINGERPRINTS_ALLOWED elements. So we
should push nothing if reaches that case. Done.

+      fingerprintName = this.i18n('lockScreenFingerprintNewName', i);
+      if (this.fingerprints_.includes(fingerprintName))
+        continue;
+      break;
+    }
+    this.push('fingerprints_', fingerprintName);
+  },
+
+  /**
+   * Deletes a fingerprint from |fingerprints_|.
+   * @private
+   */
+  onFingerprintDelete_: function(e) {
+    // TODO(sammiequon): Remove fingerprint using private API once it is ready.
+    this.splice('fingerprints_', e.model.index, 1);
+  },
+
+  /**
+   * Returns the text to be displayed for the add fingerprint button.
+   * @return {string}
+   * @private
+   */
+  getFingerprintButtonText_: function() {
+    if (this.canAddNewFingerprint_())
+      return this.i18n('lockScreenAddFingerprint');
+
+    return this.i18n('lockScreenCannotAddFingerprint',
+                     MAX_NUMBER_FINGERPRINTS_ALLOWED);
+  },
+
+  /**
+   * Checks whether another fingerprint can be added.
+   * @return {boolean}
+   * @private
+   */
+  canAddNewFingerprint_: function() {
+    return this.fingerprints_.length < MAX_NUMBER_FINGERPRINTS_ALLOWED;
+  }
+});
+})();