Set "presentation" role for page canvases (issue 14437)

web/pdf_page_view.js

@@ -837,6 +837,7 @@ class PDFPageView {
 
     const viewport = this.viewport;
     const canvas = document.createElement("canvas");
+    canvas.setAttribute("role", "presentation");
 
     // Keep the canvas hidden until the first draw callback, or until drawing
     // is complete when `!this.renderingQueue`, to prevent black flickering.