Implement translate() and translateSelf() in DOMMatrix.

Source/core/dom/DOMMatrixReadOnly.cpp

 // 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.
 
 #include "config.h"
-#include "core/dom/DOMMatrixReadOnly.h"
+#include "core/dom/DOMMatrix.h"
 
 namespace blink {
 
 bool DOMMatrixReadOnly::is2D() const
 {
     return m_is2D;
 }
 
 bool DOMMatrixReadOnly::isIdentity() const
 {
     return m_matrix.isIdentity();
 }
 
+DOMMatrix* DOMMatrixReadOnly::translate(double tx, double ty, double tz)
+{
+    return DOMMatrix::create(this)->translateSelf(tx, ty, tz);
+}
+
 } // namespace blink