Re-land "Fix external SkImageFilter caching with clips."

This reverts commit 9efd66b8451f25465abd1027e09a3bcfa7b9c554.

R=reed@google.com
TBR=reed@google.com
BUG=skia:

Author: senorblanco@chromium.org

Review URL: https://codereview.chromium.org/348903004
1 file changed