I do a lot of HTML generation just with JavaScript and am finding myself creating `index.html` files that have code that looks like this:

     <!DOCTYPE html><html><head><script src="index.js"></script></head><body></body></html>

It would be nice to be able to do:

     browserWindow.loadHTML('<!DOCTYPE html><html><head><script src="index.js"></script></head><body></body></html>');

It would be even more awesome to do:

     browserWindow.loadScript(pathToScript);

I tried to use the `preload` option for `BrowserWindow` and using `loadURL('about:blank')`, but this has an unintended side effect of not allowing you to reference other script or CSS files using relative paths.

What do you think about proposed feature?
atom/browser/api/atom_api_web_contents.cc
mate::Handle<NativeImage> image =
      NativeImage::Create(isolate(), gfx::Image::CreateFrom1xBitmap(bitmap));
  Emit("paint", dirty_rect, image);
}
void WebContents::StartPainting() {
  if (!IsOffScreen())
    return;
  auto* osr_rwhv = static_cast<OffScreenRenderWidgetHostView*>(
      web_contents()->GetRenderWidgetHostView());
  if (osr_rwhv)
    osr_rwhv->SetPainting(true);
}
void WebContents::StopPainting() {
  if (!IsOffScreen())
    return;
  auto* osr_rwhv = static_cast<OffScreenRenderWidgetHostView*>(
      web_contents()->GetRenderWidgetHostView());
  if (osr_rwhv)
    osr_rwhv->SetPainting(false);
}
bool WebContents::IsPainting() const {
  if (!IsOffScreen())
    return false;
  const auto* osr_rwhv = static_cast<OffScreenRenderWidgetHostView*>(
      web_contents()->GetRenderWidgetHostView());
  return osr_rwhv && osr_rwhv->IsPainting();
}
void WebContents::SetFrameRate(int frame_rate) {