when I drawing rectangles in low level in 2d, there is something wrong.

when I drawing rectangles in low level in 2d, the rectangles show like this:

It seems that there are shadows(inluding bright and dark blocks) from rectangles move to anthor place in the map.
this appearance is not always appears, it may usually appears in chrome when in a win7 os.

Start by reproducing the low-level 2D rectangle rendering shown in the attached image, focusing on Chrome on Windows 7 where the artifacts reportedly appear. Compare the rendered map for bright and dark blocks displaced from the rectangles; done means the intermittent shadow-like artifacts no longer occur.

Written by the indexing model from the issue text.