I was wondering if WebGL is considered stable enough to be enabled by default. It makes some PDFs render much faster and it has been off by default for a while now, so we have had quite some time to test it.

If we decide to enable WebGL by default, we should not forget to update https://github.com/mozilla/pdf.js/blob/master/extensions/chromium/preferences_schema.json#L39 as well.

/cc @yurydelendik 
/cc @Snuffleupagus (because IIRC you were testing WebGL too)

const msg = "DocException - expected a valid Error.";
        if (
          typeof PDFJSDev === "undefined" ||
          PDFJSDev.test("!PRODUCTION || TESTING")
        ) {
          unreachable(msg);
        } else {
          warn(msg);
        }
      }
      loadingTask._capability.reject(reason);
    });
    messageHandler.on("PasswordRequest", exception => {
      this._passwordCapability = createPromiseCapability();
      if (loadingTask.onPassword) {
        const updatePassword = password => {
          this._passwordCapability.resolve({
            password,
          });
        };
        try {
          loadingTask.onPassword(updatePassword, exception.code);
        } catch (ex) {
          this._passwordCapability.reject(ex);
        }
      } else {
        this._passwordCapability.reject(
          new PasswordException(exception.message, exception.code)
        );
      }