Called when an element should be painted. Pixel values passed to this function are scaled relative to view coordinates based on the value of CefScreenInfo.device_scale_factor returned from GetScreenInfo. |type| indicates whether the element is the view or the popup widget. |buffer| contains the pixel data for the whole image. |dirtyRects| contains the set of rectangles in pixel coordinates that need to be repainted. |buffer| will be |width|*|height|*4 bytes in size and represents a BGRA image with an upper-left origin. This function is only called when