Experiment to track coverage in a layer

Bug: skia:
Change-Id: I5ed334f63e64991944394dc8103092a2c6280546
Reviewed-on: https://skia-review.googlesource.com/122000
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/src/core/SkDraw_vertices.cpp b/src/core/SkDraw_vertices.cpp
index 810ded1..8c1ad1f 100644
--- a/src/core/SkDraw_vertices.cpp
+++ b/src/core/SkDraw_vertices.cpp
@@ -294,7 +294,7 @@
         // no colors[] and no texture, stroke hairlines with paint's color.
         SkPaint p;
         p.setStyle(SkPaint::kStroke_Style);
-        SkAutoBlitterChoose blitter(fDst, *fMatrix, p);
+        SkAutoBlitterChoose blitter(*this, nullptr, p);
         // Abort early if we failed to create a shader context.
         if (blitter->isNullBlitter()) {
             return;