Fixes feComponentTransfer and feColorMatrix's treatment of pixels outside input region.

Previously these two primitives would ignore pixels in their primitive region but outside the input region
which causes the filters to have incorrect results in the cases where the transformation turns transparent
pixels into visible.

BUG=330602

Review URL: https://codereview.chromium.org/116133003

git-svn-id: svn://svn.chromium.org/blink/trunk@164602 bbb929c8-8fbe-4397-9dbb-9b2b20218538