WIP: GPU-accelerated trapezoidal path renderer.

src/core/SkEdge.cpp

Index: src/core/SkEdge.cpp
diff --git a/src/core/SkEdge.cpp b/src/core/SkEdge.cpp
index f91f5f87829c45cd221dcefecfe00f6091f8f0e4..c2b2a7243650fa268fb413ba65143ae0435f066c 100644
--- a/src/core/SkEdge.cpp
+++ b/src/core/SkEdge.cpp
@@ -74,8 +74,10 @@ int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, const SkIRect* clip,
     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);
@@ -266,6 +268,8 @@ int SkQuadraticEdge::setQuadratic(const SkPoint pts[3], int shift)
 
     fQLastX = SkFDot6ToFixed(x2);
     fQLastY = SkFDot6ToFixed(y2);
+    fFirstXf    = winding < 0 ? pts[2].fX : pts[0].fX;
+    fFirstYf    = static_cast<float>(top);
 
     return this->updateQuadratic();
 }
@@ -428,6 +432,8 @@ int SkCubicEdge::setCubic(const SkPoint pts[4], int shift) {
     fCLastX = SkFDot6ToFixed(x3);
     fCLastY = SkFDot6ToFixed(y3);
 
+    fFirstXf    = winding < 0 ? pts[3].fX : pts[0].fX;
+    fFirstYf    = static_cast<float>(top);
     return this->updateCubic();
 }