The prebuilt files include `web/pdf_viewer.js` with some viewer APIs. Those are missing from type declarations.
.pipe(gulp.dest(dir + "web")),
    gulp
      .src("web/compressed.tracemonkey-pldi-09.pdf")
      .pipe(gulp.dest(dir + "web")),
  ]);
}
gulp.task(
  "generic",
  gulp.series(
    createBuildNumber,
    "locale",
    function scriptingGeneric() {
      const defines = builder.merge(DEFINES, { GENERIC: true });
      return merge([
        buildDefaultPreferences(defines, "generic/"),
        createTemporaryScriptingBundle(defines),
      ]);
    },
    function createGeneric() {
      console.log();
      console.log("### Creating generic viewer");
      const defines = builder.merge(DEFINES, { GENERIC: true });
      return buildGeneric(defines, GENERIC_DIR);
    }
  )
);
gulp.task(
  "generic-legacy",
  gulp.series(
    createBuildNumber,