Fix for empty saveLayer() with a filter which affects transparent black.

Fix for empty saveLayer() with a filter which affects transparent black.

If an saveLayer()/restore() is recorded, tilegrid/rtree will cull them
out and not draw anything. This is correct for most cases, but if the
paint in the saveLayer() is one that affects transparent black (e.g.,
it contains a color filter or image filter which affects transparent
black), this is incorrect: the filter should be applied.

Fixed by adding a no-op between the saveLayer() and restore(), and
adding a bbox node pointing at that node with the saveLayer()'s bounds.

This exposed a bug in SkPictureRecord.cpp's match(), where it would
assert if the NOOP was the last op seen. Fixed with an early-out before
calling peek_op_and_size().

BUG=skia:2254

Review URL: https://codereview.chromium.org/262363007

git-svn-id: http://skia.googlecode.com/svn/trunk@14604 2bbb7eff-a529-9590-31e7-b0007b416f81