Fix recording of saveLayout with unusual Xfermodes.

This is the root cause of a Chrome rendering bug when it tiles
layers with masks.

BUG=skia:1291,chromium:401593
R=reed@google.com, mtklein@google.com, junov@chromium.org

Author: dneto@chromium.org

Review URL: https://codereview.chromium.org/568073004
4 files changed