Convert polygerrit to es6-modules

This change replace all HTML imports with es6-modules. The only exceptions are:
* gr-app.html file, which can be deleted only after updating the
  gerrit/httpd/raw/PolyGerritIndexHtml.soy file.
* dark-theme.html which is loaded via importHref. Must be updated manually
  later in a separate change.

This change was produced automatically by ./es6-modules-converter.sh script.
No manual changes were made.

Change-Id: I0c447dd8c05757741e2c940720652d01d9fb7d67
diff --git a/polygerrit-ui/app/elements/shared/gr-label/gr-label.js b/polygerrit-ui/app/elements/shared/gr-label/gr-label.js
index b594757..c797919 100644
--- a/polygerrit-ui/app/elements/shared/gr-label/gr-label.js
+++ b/polygerrit-ui/app/elements/shared/gr-label/gr-label.js
@@ -14,20 +14,27 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-(function() {
-  'use strict';
+import '../../../scripts/bundled-polymer.js';
 
-  /**
-   * @appliesMixin Gerrit.TooltipMixin
-   * @extends Polymer.Element
-   */
-  class GrLabel extends Polymer.mixinBehaviors( [
-    Gerrit.TooltipBehavior,
-  ], Polymer.GestureEventListeners(
-      Polymer.LegacyElementMixin(
-          Polymer.Element))) {
-    static get is() { return 'gr-label'; }
-  }
+import '../../../behaviors/gr-tooltip-behavior/gr-tooltip-behavior.js';
+import {mixinBehaviors} from '@polymer/polymer/lib/legacy/class.js';
+import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
+import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
+import {PolymerElement} from '@polymer/polymer/polymer-element.js';
+import {htmlTemplate} from './gr-label_html.js';
 
-  customElements.define(GrLabel.is, GrLabel);
-})();
+/**
+ * @appliesMixin Gerrit.TooltipMixin
+ * @extends Polymer.Element
+ */
+class GrLabel extends mixinBehaviors( [
+  Gerrit.TooltipBehavior,
+], GestureEventListeners(
+    LegacyElementMixin(
+        PolymerElement))) {
+  static get template() { return htmlTemplate; }
+
+  static get is() { return 'gr-label'; }
+}
+
+customElements.define(GrLabel.is, GrLabel);
diff --git a/polygerrit-ui/app/elements/shared/gr-label/gr-label_html.js b/polygerrit-ui/app/elements/shared/gr-label/gr-label_html.js
index c1c9b23..1644c07 100644
--- a/polygerrit-ui/app/elements/shared/gr-label/gr-label_html.js
+++ b/polygerrit-ui/app/elements/shared/gr-label/gr-label_html.js
@@ -1,24 +1,21 @@
-<!--
-@license
-Copyright (C) 2016 The Android Open Source Project
+/**
+ * @license
+ * Copyright (C) 2020 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.
+ */
+import {html} from '@polymer/polymer/lib/utils/html-tag.js';
 
-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="../../../behaviors/gr-tooltip-behavior/gr-tooltip-behavior.html">
-<dom-module id="gr-label">
-  <template>
+export const htmlTemplate = html`
     <slot></slot>
-  </template>
-  <script src="gr-label.js"></script>
-</dom-module>
+`;