Replace inverse transform with Cross-product computation.

cc/quads/draw_polygon.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_QUADS_DRAW_POLYGON_H_
 #define CC_QUADS_DRAW_POLYGON_H_
 
 #include <vector>
 
 #include "cc/base/math_util.h"
@@ skipping 41 matching lines @@
   void TransformToScreenSpace(const gfx::Transform& transform);
   void TransformToLayerSpace(const gfx::Transform& inverse_transform);
 
   const std::vector<gfx::Point3F>& points() const { return points_; }
   const gfx::Vector3dF& normal() const { return normal_; }
   const DrawQuad* original_ref() const { return original_ref_; }
   int order_index() const { return order_index_; }
   bool is_split() const { return is_split_; }
   scoped_ptr<DrawPolygon> CreateCopy();
 
+  void RecomputeNormalForTesting();
+
  private:
   void ApplyTransform(const gfx::Transform& transform);
   void ApplyTransformToNormal(const gfx::Transform& transform);
 
+  void ConstructNormal();
+
   std::vector<gfx::Point3F> points_;
   // Normalized, necessitated by distance calculations and tests of coplanarity.
   gfx::Vector3dF normal_;
   // This is an index that can be used to test whether a quad comes before or
   // after another in document order, useful for tie-breaking when it comes
   // to coplanar surfaces.
   int order_index_;
   // The pointer to the original quad, which gives us all the drawing info
   // we need.
   // This DrawQuad is owned by the caller and its lifetime must be preserved
   // as long as this DrawPolygon is alive.
   const DrawQuad* original_ref_;
   bool is_split_;
 };
 
 }  // namespace cc
 
 #endif  // CC_QUADS_DRAW_POLYGON_H_