reloadWithFileText(tempFileName) {
    const { text: newText, fileSize } = this.getFileTextAndSize(tempFileName);
    const reloaded = this.reload(newText);
    this.fileSize = fileSize;
    this.ownFileText = !tempFileName || tempFileName === this.info.fileName;
    return reloaded;
  }
Reads the contents from tempFile(if supplied) or own file and sets it as contents
returns true if text changed