Remove pdf.js deprecation warnings

1. `page.getViewpoint()` now takes in JSON instead of an integer.
2. Promises are returned from loading and rendering tasks.

See https://mozilla.github.io/pdf.js/examples/index.html for more
details.

app/assets/javascripts/pdf/index.vue

@@ -39,7 +39,7 @@ export default {
           cMapUrl: '/assets/webpack/cmaps/',
           cMapPacked: true,
         })
-        .then(this.renderPages)
+        .promise.then(this.renderPages)
         .then(pages => {
           this.pages = pages;
           this.$emit('pdflabload');

app/assets/javascripts/pdf/page/index.vue

@@ -18,7 +18,7 @@ export default {
   },
   computed: {
     viewport() {
-      return this.page.getViewport(this.scale);
+      return this.page.getViewport({ scale: this.scale });
     },
     context() {
       return this.$refs.canvas.getContext('2d');
@@ -36,7 +36,7 @@ export default {
     this.rendering = true;
     this.page
       .render(this.renderContext)
-      .then(() => {
+      .promise.then(() => {
         this.rendering = false;
       })
       .catch(error => {

changelogs/unreleased/sh-remove-pdfjs-deprecations.yml

+---
+title: Remove pdf.js deprecation warnings
+merge_request: 31253
+author:
+type: fixed

spec/javascripts/pdf/page_spec.js

@@ -17,7 +17,7 @@ describe('Page component', () => {
     pdfjsLib.GlobalWorkerOptions.workerSrc = workerSrc;
     pdfjsLib
       .getDocument(testPDF)
-      .then(pdf => pdf.getPage(1))
+      .promise.then(pdf => pdf.getPage(1))
       .then(page => {
         testPage = page;
       })
@@ -31,7 +31,8 @@ describe('Page component', () => {
 
   it('renders the page when mounting', done => {
     const promise = Promise.resolve();
-    spyOn(testPage, 'render').and.callFake(() => promise);
+    spyOn(testPage, 'render').and.returnValue({ promise });
+
     vm = mountComponent(Component, {
       page: testPage,
       number: 1,