Add gr-account-list

This new element is a more general variation of gr-reviewer-list.
The user can enter additions, which are staged in the list with
a distinct style and are removable. These pending additions can
then be committed later in response to some other user action.

Change-Id: I043665b572606d8e49b97aeaee9740a1236cd923

polygerrit-ui/app/elements/change/gr-account-list/gr-account-list.html

@@ -0,0 +1,52 @@
+<!--
+Copyright (C) 2016 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+<link rel="import" href="../../../bower_components/polymer/polymer.html">
+<link rel="import" href="../../shared/gr-account-chip/gr-account-chip.html">
+
+<dom-module id="gr-account-list">
+  <template>
+    <style>
+      gr-account-chip {
+        display: inline-block;
+      }
+      .group {
+        --account-label-suffix: ' (group)';
+      }
+      .pending-add {
+        font-style: italic;
+      }
+    </style>
+    <template id="chips" is="dom-repeat" items="[[accounts]]" as="account">
+      <gr-account-chip
+          account="[[account]]"
+          class$="[[_computeChipClass(account)]]"
+          data-account-id$="[[account._account_id]]"
+          removable="[[_computeRemovable(account)]]">
+      </gr-account-chip>
+    </template>
+    <gr-account-entry
+        borderless
+        hidden$="[[readonly]]"
+        id="entry"
+        change="[[change]]"
+        filter="[[filter]]"
+        placeholder="[[placeholder]]"
+        on-add="_handleAdd">
+    </gr-account-entry>
+  </template>
+  <script src="gr-account-list.js"></script>
+</dom-module>