Correct normal computation for inverted polygons.

ui/gfx/transform.h

Index: ui/gfx/transform.h
diff --git a/ui/gfx/transform.h b/ui/gfx/transform.h
index 75c4797744a4310c569751bfc4380224286d5b84..5bd74b51d6577eb136cc84cd4e88a013798b7a4e 100644
--- a/ui/gfx/transform.h
+++ b/ui/gfx/transform.h
@@ -198,6 +198,9 @@ class GFX_EXPORT Transform {
   // Applies the transformation to the point.
   void TransformPoint(Point* point) const;
 
+  // Applies the transformation to the vector.
+  void TransformVector(Vector3dF* vector) const;
+
   // Applies the reverse transformation on the point. Returns true if the
   // transformation can be inverted.
   bool TransformPointReverse(Point3F* point) const;
@@ -266,6 +269,9 @@ class GFX_EXPORT Transform {
   void TransformPointInternal(const SkMatrix44& xform,
                               Point3F* point) const;
 
+  void TransformVectorInternal(const SkMatrix44& xform,
+                               Vector3dF* vector) const;
+
   SkMatrix44 matrix_;
 
   // copy/assign are allowed.