Fix repaint of background-image blur filter.

Pixel-moving filters in Skia (e.g., blur, drop-shadow) have computation
to expand the clip rect by the appropriate amount, so that the source
primitive is drawn larger to accommodate the filter outsets.

background-image code was intersecting the destRect of Image::drawTiled()
with the repaint rect, which defeats the Skia adjustment. Remove the
clipping, so that Skia can handle it correctly at playback time.

BUG=415106
R=junov@chromium.org

Review URL: https://codereview.chromium.org/593453002

git-svn-id: svn://svn.chromium.org/blink/trunk@182448 bbb929c8-8fbe-4397-9dbb-9b2b20218538