Fix some typescript compile errors

elements/change-list/gr-change-list/gr-change-list.ts:481:3 - error TS4053: Return type of public method from exported class has or is using name 'GrChangeListItem' from external module "elements/change-list/gr-change-list-item/gr-change-list-item" but cannot be named.

481   _getListItems() {
      ~~~~~~~~~~~~~

elements/change/gr-download-dialog/gr-download-dialog.ts:101:3 - error TS4053: Return type of public method from exported class has or is using name 'PaperTabsElement' from external module "goog:polymer.paperTabs.paperTabs" but cannot be named.

101   getFocusStops() {
      ~~~~~~~~~~~~~

elements/shared/gr-js-api-interface/gr-plugin-action-context.ts:66:3 - error TS4053: Return type of public method from exported class has or is using name 'PaperInputElement' from external module "goog:polymer.paperInput.paperInput" but cannot be named.

66   textfield() {
     ~~~~~~~~~

Change-Id: I359562c0ad6f4cb84e1919e6f7ee4b3883ba7438

polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item.ts

diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item.ts b/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item.ts
index 531e3dc..e476522 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item.ts
@@ -60,7 +60,7 @@
 const PRIMARY_REVIEWERS_COUNT = 2;
 
 @customElement('gr-change-list-item')
-class GrChangeListItem extends ChangeTableMixin(
+export class GrChangeListItem extends ChangeTableMixin(
   GestureEventListeners(LegacyElementMixin(PolymerElement))
 ) {
   static get template() {

polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.ts

diff --git a/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.ts b/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.ts
index 9f2ff51..eb8d4cb 100644
--- a/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog.ts
@@ -28,6 +28,7 @@
 import {GrDownloadCommands} from '../../shared/gr-download-commands/gr-download-commands';
 import {GrButton} from '../../shared/gr-button/gr-button';
 import {hasOwnProperty} from '../../../utils/common-util';
+import {GrOverlayStops} from '../../shared/gr-overlay/gr-overlay';
 
 export interface GrDownloadDialog {
   $: {
@@ -96,7 +97,7 @@
     }
   }
 
-  getFocusStops() {
+  getFocusStops(): GrOverlayStops {
     return {
       start: this.$.downloadCommands.$.downloadTabs,
       end: this.$.closeButton,

polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-action-context.ts

diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-action-context.ts b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-action-context.ts
index 4366dd5..b3f4987 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-action-context.ts
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-plugin-action-context.ts
@@ -63,7 +63,7 @@
     window.location.reload();
   }
 
-  textfield() {
+  textfield(): HTMLElement {
     return document.createElement('paper-input');
   }