Dispatch the `pagerendered` event when zooming is only done with CSS (issue 6463)

In my opinion, this event shouldn't be dispatched in `PDFPageView.cssTransform`, since that would cause *two* events to be fired when "normal" zooming is used (once in `PDFPageView.cssTransform`, and once in `PDFPageView.draw`).

Fixes 6463.

web/pdf_page_view.js

@@ -181,6 +181,14 @@ var PDFPageView = (function PDFPageViewClosure() {
         if (PDFJS.useOnlyCssZoom ||
             (this.hasRestrictedScaling && isScalingRestricted)) {
           this.cssTransform(this.canvas, true);
+
+          var event = document.createEvent('CustomEvent');
+          event.initCustomEvent('pagerendered', true, true, {
+            pageNumber: this.id,
+            cssTransform: true,
+          });
+          this.div.dispatchEvent(event);
+
           return;
         }
         if (!this.zoomLayer) {
@@ -421,7 +429,8 @@ var PDFPageView = (function PDFPageViewClosure() {
         }
         var event = document.createEvent('CustomEvent');
         event.initCustomEvent('pagerendered', true, true, {
-          pageNumber: self.id
+          pageNumber: self.id,
+          cssTransform: false,
         });
         div.dispatchEvent(event);
 //#if GENERIC