Implement translate() and translateSelf() in DOMMatrix.

Source/core/dom/DOMMatrixReadOnly.h

Index: Source/core/dom/DOMMatrixReadOnly.h
diff --git a/Source/core/dom/DOMMatrixReadOnly.h b/Source/core/dom/DOMMatrixReadOnly.h
index fee20eb05722897ec404f52400cc4aeda2f9afeb..92b60f4d92e36b94015b94a4a619f110988910e3 100644
--- a/Source/core/dom/DOMMatrixReadOnly.h
+++ b/Source/core/dom/DOMMatrixReadOnly.h
@@ -11,6 +11,8 @@
 
 namespace blink {
 
+class DOMMatrix;
+
 class DOMMatrixReadOnly : public GarbageCollected<DOMMatrixReadOnly>, public ScriptWrappableBase {
 public:
     double a() const { return m_matrix.m11(); }
@@ -40,6 +42,8 @@ public:
     bool is2D() const;
     bool isIdentity() const;
 
+    DOMMatrix* translate(double tx, double ty, double tz = 0);
+
     const TransformationMatrix& matrix() const { return m_matrix; }
 
     void trace(Visitor*) { }