WIP: GPU-accelerated trapezoidal path renderer.

src/core/SkEdge.h

Index: src/core/SkEdge.h
diff --git a/src/core/SkEdge.h b/src/core/SkEdge.h
index db6f43085dadf88bd4b28cd128a2280d86935d92..f9175591df9b608d5392d25bf57253d9dec707c3 100644
--- a/src/core/SkEdge.h
+++ b/src/core/SkEdge.h
@@ -29,6 +29,8 @@ struct SkEdge {
 
     SkFixed fX;
     SkFixed fDX;
+    float   fFirstXf;      // only used for trapezoidal renderer
+    float   fFirstYf;      // only used for trapezoidal renderer
     int32_t fFirstY;
     int32_t fLastY;
     int8_t fCurveCount;    // only used by kQuad(+) and kCubic(-)
@@ -122,8 +124,10 @@ int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, int shift) {
     const SkFDot6 dy  = SkEdge_Compute_DY(top, y0);
 
     fX          = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy));   // + SK_Fixed1/2
+    fFirstXf    = winding < 0 ? p1.fX : p0.fX;
     fDX         = slope;
     fFirstY     = top;
+    fFirstYf    = static_cast<float>(top);
     fLastY      = bot - 1;
     fCurveCount = 0;
     fWinding    = SkToS8(winding);