Implement *multiply*() methods in DOMMatrix.

Source/core/dom/DOMMatrix.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/DOMMatrix.h"
 
 namespace blink {
 
 DOMMatrix* DOMMatrix::create()
@@ skipping 11 matching lines @@
     m_matrix = matrix;
     m_is2D = is2D;
 }
 
 void DOMMatrix::setIs2D(bool value)
 {
     if (m_is2D)
         m_is2D = value;
 }
 
+DOMMatrix* DOMMatrix::multiplySelf(DOMMatrix* other)
+{
+    if (!other->is2D())
+        m_is2D = false;
+
+    m_matrix = m_matrix * other->matrix();
+
+    return this;
+}
+
+DOMMatrix* DOMMatrix::preMultiplySelf(DOMMatrix* other)
+{
+    if (!other->is2D())
+        m_is2D = false;
+
+    m_matrix = other->matrix() * m_matrix;
+
+    return this;
+}
+
 DOMMatrix* DOMMatrix::translateSelf(double tx, double ty, double tz)
 {
     if (!tx && !ty && !tz)
         return this;
 
     if (tz)
         m_is2D = false;
 
     if (m_is2D)
         m_matrix.translate(tx, ty);
@@ skipping 32 matching lines @@
     else
         m_matrix.scale3d(sx, sy, sz);
 
     if (hasTranslation)
         translateSelf(-ox, -oy, -oz);
 
     return this;
 }
 
 } // namespace blink