code: function extractMetaNodes(profile) {
          const topLevelNodes = profile.resultRoot.children;
          for (let i = 0; i < topLevelNodes.length && !(profile.gcNode && profile.programNode && profile.idleNode); i++) {
              const node = topLevelNodes[i];
              if (node.functionName === '(garbage collector)')
                  profile.gcNode = node;
              else if (node.functionName === '(program)')
                  profile.programNode = node;
              else if (node.functionName === '(idle)')
                  profile.idleNode = node;
          }
      }
docs: *
  @param {object} profile
  @description 找出 gc / program / idle 等属性