For #11961: collect telemetry on all unique unsupported features that…

… trigger fallback error.

This expands upon the telemetry we are collecting that shows the fallback error.

web/app.js

@@ -864,11 +864,27 @@ const PDFViewerApplication = {
  .catch(downloadByUrl); // Error occurred, try downloading with the URL.
  },
 
+ _recordFallbackErrorTelemetry(featureId) {
+ if (
+ typeof PDFJSDev === "undefined" ||
+ PDFJSDev.test("MOZCENTRAL || GENERIC")
+ ) {
+ this.externalServices.reportTelemetry({
+ type: "unsupportedFeature",
+ featureId,
+ });
+ }
+ },
+
  fallback(featureId) {
  if (
  typeof PDFJSDev === "undefined" ||
  PDFJSDev.test("MOZCENTRAL || GENERIC")
  ) {
+ if (featureId) {
+ this._recordFallbackErrorTelemetry(featureId);
+ }
+
  // For PDFs that contain script and form errors, we should only trigger
  // the fallback once the user has interacted with the page.
  if (this._delayedFallbackFeatureIds.length >= 1 && this._hasInteracted) {
@@ -1247,6 +1263,7 @@ const PDFViewerApplication = {
  }
  console.warn("Warning: JavaScript is not supported");
  this._delayedFallbackFeatureIds.push(UNSUPPORTED_FEATURES.javaScript);
+ this._recordFallbackErrorTelemetry(UNSUPPORTED_FEATURES.javaScript);
  return true;
  });
 
@@ -1329,6 +1346,7 @@ const PDFViewerApplication = {
  if (info.IsAcroFormPresent) {
  console.warn("Warning: AcroForm/XFA is not supported");
  this._delayedFallbackFeatureIds.push(UNSUPPORTED_FEATURES.forms);
+ this._recordFallbackErrorTelemetry(UNSUPPORTED_FEATURES.forms);
  }
 
  if (