GitLab

Allow single-pass filters (which use asNewEffect()) to participate in the image filter DAG.  This was done by introducing the SkSinglePassImageFilter abstract base class, which implements canFilterImageGPU() and filterImageGPU() on behalf of the derived class.  The derived class still only needs to asNewEffect().  This allows us to recurse on the filter input in SkSinglePassImageFilter::onFilterImageGPU().  It also allows us to remove any knowledge of single-pass image filters from SkGpuDevice and from the SkImageFilter base class as well.

BUG=

Review URL: https://codereview.chromium.org/13602013

git-svn-id: http://skia.googlecode.com/svn/trunk@8563 2bbb7eff-a529-9590-31e7-b0007b416f81