Implement filter primitive subregion on accelerated reference filters for FEColorMatrix, FEGaussianBlur and FE*Lighting. This patch also adds crop tests for all the filters, both software and hardware versions. The software results are correct; bringing the remainder of the hardware results into alignment with software results will be the work of future patches (Skia and Blink-side).

The patch adds a crop offset to the SkiaImageFilterBuilder, which is used to communicate the offset computed by the Blink filter chain when inflating its results for filter bounds. This code may be removed in the future once Skia takes on this responsibility and knows how much each filter inflates its result.

BUG=229910

Review URL: https://chromiumcodereview.appspot.com/22794007

git-svn-id: svn://svn.chromium.org/blink/trunk@157529 bbb929c8-8fbe-4397-9dbb-9b2b20218538