code: function StackFrame(className, methodName, fileName, lineNumber, columnNumber) {
    if (className) {
      this.class_name = className;
    }
    if (methodName) {
      this.method_name = methodName;
    }
    if (fileName) {
      this.file_name = fileName;
    }
    if (typeof lineNumber === 'number') {
      this.line_number = lineNumber;
    }
    if (typeof columnNumber === 'number') {
      this.column_number = columnNumber;
    }
  }
docs: Trace API expects stack frames to be a JSON string with the following
  structure:
  STACK_TRACE := { "stack_frame" : [ FRAMES ] }
  FRAMES := { "class_name" : CLASS_NAME, "file_name" : FILE_NAME,
  "line_number" : LINE_NUMBER, "method_name" : METHOD_NAME }*
  
  While the API doesn't expect a columnNumber at this point, it does accept,
  and ignore it.
  
  @param {string|undefined} className
  @param {string|undefined} methodName
  @param {string|undefined} fileName
  @param {number|undefined} lineNumber
  @param {number|undefined} columnNumber
  @constructor @private