Draw thin slices of an image w/ anti-aliasing for 2D <canvas>

Add a GraphicsContext-scoped flag that allows anti-aliasing of
(all) image-geometry to be enabled in a selective manner.
Enable this behavior for CanvasRenderingContext2D.
When this flag is set, image geometry that would drawn as very
thin (< 1 device pixel wide/high) will be anti-aliased.

BUG=352611

Review URL: https://codereview.chromium.org/210043004

git-svn-id: svn://svn.chromium.org/blink/trunk@170671 bbb929c8-8fbe-4397-9dbb-9b2b20218538