Page.addScriptToEvaluateOnLoad

{
  "name": "addScriptToEvaluateOnLoad",
  "parameters": [
    {
      "name": "scriptSource",
      "type": "string"
    }
  ],
  "returns": [
    {
      "name": "identifier",
      "$ref": "ScriptIdentifier",
      "description": "Identifier of the added script."
    }
  ],
  "experimental": true
}