Implement addPath() method for Path object

Source/core/html/canvas/Path.idl

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2012, 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 16 matching lines @@
  */
 
 [
     RuntimeEnabled=ExperimentalCanvasFeatures,
     Constructor,
     Constructor(Path path),
     Constructor(DOMString text),
     ImplementedAs=DOMPath
 ] interface Path {
 
+    [RaisesException] void addPath(Path? path, SVGMatrix? transform);
+
     // FIXME: These methods should be shared with CanvasRenderingContext2D in the CanvasPathMethods interface.
     void closePath();
     void moveTo([Default=Undefined] optional float x,
                 [Default=Undefined] optional float y);
     void lineTo([Default=Undefined] optional float x,
                 [Default=Undefined] optional float y);
     void quadraticCurveTo([Default=Undefined] optional float cpx,
                           [Default=Undefined] optional float cpy,
                           [Default=Undefined] optional float x,
                           [Default=Undefined] optional float y);
@@ skipping 12 matching lines @@
               [Default=Undefined] optional float y,
               [Default=Undefined] optional float width,
               [Default=Undefined] optional float height);
     [RaisesException] void arc([Default=Undefined] optional float x,
              [Default=Undefined] optional float y,
              [Default=Undefined] optional float radius,
              [Default=Undefined] optional float startAngle,
              [Default=Undefined] optional float endAngle,
              [Default=Undefined] optional boolean anticlockwise);
 };