def capture_entire_page_screenshot_to_string(self,kwargs):
return self.get_string("<STR_LIT>", [kwargs,])<EOL>
Downloads a screenshot of the browser current window canvas to a
based 64 encoded PNG file. The \ *entire* windows canvas is captured,
including parts rendered outside of the current view port.

Currently this only works in Mozilla and when running in chrome mode.

'kwargs' is A kwargs string that modifies the way the screenshot is captured. Example: "background=#CCFFDD". This may be useful to set for capturing screenshots of less-than-ideal layouts, for example where absolute positioning causes the calculation of the canvas dimension to fail and a black background is exposed  (possibly obscuring black text).