Add back captureScreenshotAsBase64

[BlackHC]

The sync webdriver provides both captureScreenshot and captureScreenshotAsBase64.

Atm:

  /// Take a screenshot of the current page as PNG.
  Stream<int> captureScreenshot() async* {
    var encoded = await getRequest('screenshot');
    yield* new Stream.fromIterable(CryptoUtils.base64StringToBytes(encoded));
  }

This could be split up again into two methods.

[DrMarcII]

What is the use case?

[BlackHC]

We use it to log a screenshot in our html log using an embedded "data:" URL. It doesn't really seem to make sense to decode from base64 to encode right again. What do you think?

[DrMarcII]

Feel free to send a PR.