use SkPoint, creating an alias for GrPoint

http://codereview.appspot.com/4498041/



git-svn-id: http://skia.googlecode.com/svn/trunk@1268 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/src/GrMatrix.cpp b/gpu/src/GrMatrix.cpp
index 92a38ee..b169d19 100644
--- a/gpu/src/GrMatrix.cpp
+++ b/gpu/src/GrMatrix.cpp
@@ -631,7 +631,7 @@
         if (maxStretch > 0) {
             maxStretch = GrMul(GR_Scalar1 + GR_Scalar1 / 100, maxStretch);
         }
-        GrPoint origin = a.mapPoint(GrPoint(0,0));
+        GrPoint origin = a.mapPoint(GrPoint::Make(0,0));
 
         for (int j = 0; j < 9; ++j) {
             int mask, origMask = a.fTypeMask;
@@ -668,8 +668,8 @@
             a.mapPerspective(&t2, &pt, 1);   // full mult
             GrAssert(t0 == t1 && t1 == t2);
             if (maxStretch >= 0.f) {
-                GrVec vec;
-                vec.setBetween(t0, origin);
+                GrVec vec = origin - t0;
+//                vec.setBetween(t0, origin);
                 GrScalar stretch = vec.length() / pt.distanceToOrigin();
                 GrAssert(stretch <= maxStretch);
             }