Implement translate() and translateSelf() in DOMMatrix.

Source/core/dom/DOMMatrixReadOnly.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 DOMMatrixReadOnly_h
 #define DOMMatrixReadOnly_h
 
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
+class DOMMatrix;
+
 class DOMMatrixReadOnly : public GarbageCollected<DOMMatrixReadOnly> {
 public:
     double a() const { return m11(); }
     double b() const { return m12(); }
     double c() const { return m21(); }
     double d() const { return m22(); }
     double e() const { return m41(); }
     double f() const { return m42(); }
 
     double m11() const { return m_matrix[0][0]; }
     double m12() const { return m_matrix[0][1]; }
     double m13() const { return m_matrix[0][2]; }
     double m14() const { return m_matrix[0][3]; }
     double m21() const { return m_matrix[1][0]; }
     double m22() const { return m_matrix[1][1]; }
     double m23() const { return m_matrix[1][2]; }
     double m24() const { return m_matrix[1][3]; }
     double m31() const { return m_matrix[2][0]; }
     double m32() const { return m_matrix[2][1]; }
     double m33() const { return m_matrix[2][2]; }
     double m34() const { return m_matrix[2][3]; }
     double m41() const { return m_matrix[3][0]; }
     double m42() const { return m_matrix[3][1]; }
     double m43() const { return m_matrix[3][2]; }
     double m44() const { return m_matrix[3][3]; }
 
     bool is2D() const;
     bool isIdentity() const;
 
+    DOMMatrix* translate(double tx, double ty, double tz = 0);
+
     void trace(Visitor*) { }
 
 protected:
     double m_matrix[4][4];
     bool m_is2D;
 };
 
 } // namespace blink
 
 #endif