Make body element background image use correct interpolation quality.

When the body background is propagated to the viewport, its
interpolation quality should still be based on the style of the body
element.

BUG=466272

Review URL: https://codereview.chromium.org/1025563002

git-svn-id: svn://svn.chromium.org/blink/trunk@192577 bbb929c8-8fbe-4397-9dbb-9b2b20218538
5 files changed