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### Issue Details

* **Electron Version:**
  * 10.1.3
* **Operating System:**
  * win7 sp1 x64

- without worldSafeExecuteJavaScript, `(webFrame|webContents).executeJavaScript('new Promise(resolve => setTimeout(() => resolve(2), 3000));')` works as expected; the executeJavaScript promise waits for the eval promise.
- in the case of webFrame the evaled promise is returned raw
- in the case of webContents the promise is marshaled
- with worldSafeExecuteJavaScript, both error with: "An object could not be cloned"
- webContents should continue marshaling promises, otherwise its an unnecessary breaking change
- webFrame should marshal promises for consistency with webContents
- the clone restriction would be on the promise resolve value

### To Reproduce
`(webFrame|webContents).executeJavaScript('new Promise(resolve => setTimeout(() => resolve(2), 3000));')`


shell/renderer/api/electron_api_web_frame.cc
v8::Local<v8::Value> val,
                     blink::WebDocument::CSSOrigin* out) {
    std::string css_origin;
    if (!ConvertFromV8(isolate, val, &css_origin))
      return false;
    if (css_origin == "user") {
      *out = blink::WebDocument::CSSOrigin::kUserOrigin;
    } else if (css_origin == "author") {
      *out = blink::WebDocument::CSSOrigin::kAuthorOrigin;
    } else {
      return false;
    }
    return true;
  }
};
}  
namespace electron {
namespace api {
namespace {
content::RenderFrame* GetRenderFrame(v8::Local<v8::Value> value) {