Implement translate() and translateSelf() in DOMMatrix.

Source/core/dom/DOMMatrix.h

Index: Source/core/dom/DOMMatrix.h
diff --git a/Source/core/dom/DOMMatrix.h b/Source/core/dom/DOMMatrix.h
index f125002128070016fdef08d375ae52c3c4a1320b..03ca8d013670cf082e9f63945b8f74fb714cd035 100644
--- a/Source/core/dom/DOMMatrix.h
+++ b/Source/core/dom/DOMMatrix.h
@@ -38,6 +38,8 @@ public:
     void setM43(double value) { m_matrix.setM43(value); setIs2D(!value); }
     void setM44(double value) { m_matrix.setM44(value); setIs2D(value != 1); }
 
+    DOMMatrix* translateSelf(double tx, double ty, double tz = 0);
+
 private:
     DOMMatrix(const TransformationMatrix&, bool is2D = true);