Move SkRecordComputeLayers and CollectLayers into SkRecordDraw.cpp

Rather then exposing parts of FillBounds (as in Expose FillBounds to allow GrPictureUtils::CollectLayers to be layered on top of it - https://codereview.chromium.org/698643002/), this CL moves CollectLayers into SkRecordDraw.cpp to accomplish the layering.

Review URL: https://codereview.chromium.org/716913003
6 files changed