Force values to 0.0f in QuadUVMatrix::set

src/gpu/GrPathUtils.cpp

Index: src/gpu/GrPathUtils.cpp
diff --git a/src/gpu/GrPathUtils.cpp b/src/gpu/GrPathUtils.cpp
index 0fd8b0e8829a0032361205bb6397fb9cc79b06ae..fcb32cbd9a033f5761cd3d05e4058cf21df58e01 100644
--- a/src/gpu/GrPathUtils.cpp
+++ b/src/gpu/GrPathUtils.cpp
@@ -267,9 +267,7 @@ void GrPathUtils::QuadUVMatrix::set(const SkPoint qPts[3]) {
         double scale = 1.0/det;
 
         // compute adjugate matrix
-        double a0, a1, a2, a3, a4, a5, a6, a7, a8;
-        a0 = y1-y2;
-        a1 = x2-x1;
+        double a2, a3, a4, a5, a6, a7, a8;
         a2 = x1*y2-x2*y1;
 
         a3 = y2-y0;
@@ -290,15 +288,11 @@ void GrPathUtils::QuadUVMatrix::set(const SkPoint qPts[3]) {
         m[SkMatrix::kMScaleY] = (float)(a7*scale);
         m[SkMatrix::kMTransY] = (float)(a8*scale);
 
-        m[SkMatrix::kMPersp0] = (float)((a0 + a3 + a6)*scale);
-        m[SkMatrix::kMPersp1] = (float)((a1 + a4 + a7)*scale);
+        // kMPersp0 & kMPersp1 should algebraically be zero
+        m[SkMatrix::kMPersp0] = 0.0f;
+        m[SkMatrix::kMPersp1] = 0.0f;
         m[SkMatrix::kMPersp2] = (float)((a2 + a5 + a8)*scale);
 
-        // The matrix should not have perspective.
-        SkDEBUGCODE(static const SkScalar gTOL = 1.f / 100.f);
-        SkASSERT(SkScalarAbs(m.get(SkMatrix::kMPersp0)) < gTOL);
-        SkASSERT(SkScalarAbs(m.get(SkMatrix::kMPersp1)) < gTOL);
-
         // It may not be normalized to have 1.0 in the bottom right
         float m33 = m.get(SkMatrix::kMPersp2);
         if (1.f != m33) {