At first, mask didn't affect on background, if filter was applied on it.
This bug occurred because of loss of information about
original background texture. So I added necessary information to shader
and fixed this bug.

R=danakj@chromium.org, enne@chromium.org

TEST=LayerTreeHostMasksForBackgroundFiltersPixelTest.MaskOfLayerWithBackgroundFilter

Review URL: https://codereview.chromium.org/959283004

Cr-Commit-Position: refs/heads/master@{#319323}