Change all components to use the service for rest-api-interface

Change-Id: I3acf9269ff43f463aca59aa10ca131b037cede9d
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts
index e0333cc..c30feeb 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts
@@ -20,7 +20,6 @@
 import '../../shared/gr-button/gr-button';
 import '../../shared/gr-rest-api-interface/gr-rest-api-interface';
 import {DiffViewMode} from '../../../constants/constants';
-import {RestApiService} from '../../../services/services/gr-rest-api/gr-rest-api';
 import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
 import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
 import {PolymerElement} from '@polymer/polymer/polymer-element';
@@ -28,12 +27,7 @@
 import {customElement, property} from '@polymer/decorators';
 import {IronA11yAnnouncer} from '@polymer/iron-a11y-announcer/iron-a11y-announcer';
 import {FixIronA11yAnnouncer} from '../../../types/types';
-
-export interface GrDiffModeSelector {
-  $: {
-    restAPI: RestApiService & Element;
-  };
-}
+import {appContext} from '../../../services/app-context';
 
 @customElement('gr-diff-mode-selector')
 export class GrDiffModeSelector extends GestureEventListeners(
@@ -53,6 +47,8 @@
   @property({type: Boolean})
   saveOnChange = false;
 
+  private readonly restApiService = appContext.restApiService;
+
   attached() {
     ((IronA11yAnnouncer as unknown) as FixIronA11yAnnouncer).requestAvailability();
   }
@@ -62,7 +58,7 @@
    */
   setMode(newMode: DiffViewMode) {
     if (this.saveOnChange && this.mode && this.mode !== newMode) {
-      this.$.restAPI.savePreferences({diff_view: newMode});
+      this.restApiService.savePreferences({diff_view: newMode});
     }
     this.mode = newMode;
     let annoucement;