Remove window.Plugin and use import instead

Also moved the shared api element to gr-js-api-interface-element,
that's also where the componenet defined.

Change-Id: Icf4f48be3e3ce843a4b0ec6491aaa5a27342b3d8

polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-reply-js-api.js

@@ -15,18 +15,19 @@
  * limitations under the License.
  */
 
+import {sharedApiElement} from './gr-js-api-interface-element.js';
+
 /**
  * GrChangeReplyInterface, provides a set of handy methods on reply dialog.
  */
 export class GrChangeReplyInterface {
   constructor(plugin) {
     this.plugin = plugin;
-    this._sharedApiEl = Plugin._sharedAPIElement;
   }
 
   get _el() {
-    return this._sharedApiEl.getElement(
+    return sharedApiElement.getElement(
-        this._sharedApiEl.Element.REPLY_DIALOG);
+        sharedApiElement.Element.REPLY_DIALOG);
   }
 
   getLabelValue(label) {

polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface-element.js

@@ -327,3 +327,6 @@ class GrJsApiInterface extends GestureEventListeners(
 }
 
 customElements.define(GrJsApiInterface.is, GrJsApiInterface);
+
+// The shared api element used across components
+export const sharedApiElement = document.createElement('gr-js-api-interface');

polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-loader.js

@@ -16,15 +16,13 @@ import {appContext} from '../../../services/app-context.js';
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import './gr-api-utils.js';
 import {importHref} from '../../../scripts/import-href.js';
-
 import {
   PLUGIN_LOADING_TIMEOUT_MS,
   PRELOADED_PROTOCOL,
   getPluginNameFromUrl,
 } from './gr-api-utils.js';
-
+import {Plugin} from './gr-public-js-api.js';
 import {getBaseUrl} from '../../../utils/url-util.js';
 
 /**

polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js

@@ -32,6 +32,7 @@ import {GrSettingsApi} from '../../plugins/gr-settings-api/gr-settings-api.js';
 import {GrStylesApi} from '../../plugins/gr-styles-api/gr-styles-api.js';
 import {GrPluginActionContext} from './gr-plugin-action-context.js';
 import {pluginEndpoints} from './gr-plugin-endpoints.js';
+import {sharedApiElement} from './gr-js-api-interface-element.js';
 
 import {
   PRELOADED_PROTOCOL,
@@ -162,7 +163,7 @@ export class Plugin {
   }
 
   on(eventName, callback) {
-    Plugin._sharedAPIElement.addEventCallback(eventName, callback);
+    sharedApiElement.addEventCallback(eventName, callback);
   }
 
   url(opt_path) {
@@ -219,8 +220,8 @@ export class Plugin {
   changeActions() {
     return new GrChangeActionsInterface(
         this,
-        Plugin._sharedAPIElement.getElement(
+        sharedApiElement.getElement(
-            Plugin._sharedAPIElement.Element.CHANGE_ACTIONS
+            sharedApiElement.Element.CHANGE_ACTIONS
         )
     );
   }
@@ -313,8 +314,6 @@ export class Plugin {
   }
 }
 
-Plugin._sharedAPIElement = document.createElement('gr-js-api-interface');
-
 // TODO: should be removed soon after all core plugins moved away from it.
 const deprecatedAPI = {
   _loadedGwt: () => {},
@@ -432,6 +431,3 @@ const deprecatedAPI = {
     );
   },
 };
-
-// TODO: Remove once no longer rely on global Plugin
-window.Plugin = Plugin;