Do not repaint the overhang linen texture every frame

Instead of adding a layer for the linen texture (which needs to
be painted every frame) specify a gutter texture for the layer
tree to use.

Remove the layer into which the linen texture was being painted.

BUG=133097

Review URL: https://codereview.chromium.org/27748005

git-svn-id: svn://svn.chromium.org/blink/trunk@160257 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove the overflow related functions from RenderLayer

I inspected the call sites for NULL ScrollableArea and they
should be safe. Also removed RenderLayer::scroll().

BUG=260899

Review URL: https://codereview.chromium.org/28953004

git-svn-id: svn://svn.chromium.org/blink/trunk@160258 bbb929c8-8fbe-4397-9dbb-9b2b20218538