Add localToAbsoluteTransform and localToAncestorTransform.

third_party/WebKit/Source/platform/transforms/TransformationMatrix.h

 /*
  * Copyright (C) 2005, 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 301 matching lines @@
     {
         return m13() == 0 && m14() == 0 && m23() == 0 && m24() == 0
             && m31() == 0 && m32() == 0 && m33() == 1 && m34() == 0 && m43() == 0 && m44() == 1;
     }
 
     // Throw away the non-affine parts of the matrix (lossy!)
     void makeAffine();
 
     AffineTransform toAffineTransform() const;
 
+    // Flatten into a 2-D transformation (lossy!)
+    void flattenTo2d();

[chrishtr, 2016/03/15 23:06:42]

Add a note that this is the same as gfx::TransformTo2d, and refer to the more
extensive comments there.

Also remove the note about lossy, or just rephrase to note that it is
a non-invertible transform.

[dmazzoni, 2016/03/16 05:42:01]

Done.

+
     bool operator==(const TransformationMatrix& m2) const
     {
         return m_matrix[0][0] == m2.m_matrix[0][0]
             && m_matrix[0][1] == m2.m_matrix[0][1]
             && m_matrix[0][2] == m2.m_matrix[0][2]
             && m_matrix[0][3] == m2.m_matrix[0][3]
             && m_matrix[1][0] == m2.m_matrix[1][0]
             && m_matrix[1][1] == m2.m_matrix[1][1]
             && m_matrix[1][2] == m2.m_matrix[1][2]
             && m_matrix[1][3] == m2.m_matrix[1][3]
@@ skipping 87 matching lines @@
     Matrix4 m_matrix;
 };
 
 // Redeclared here to avoid ODR issues.
 // See platform/testing/TransformPrinters.h.
 void PrintTo(const TransformationMatrix&, std::ostream*);
 
 } // namespace blink
 
 #endif // TransformationMatrix_h