Add null check to fill, stroke, clip method

Source/core/html/canvas/CanvasRenderingContext2D.idl

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 60 matching lines @@
     void lineTo(float x, float y);
     void quadraticCurveTo(float cpx, float cpy, float x, float y);
     void bezierCurveTo(float cp1x, float cp1y, float cp2x, float cp2y, float x, float y);
     [RaisesException] void arcTo(float x1, float y1, float x2, float y2, float radius);
     void rect(float x, float y, float width, float height);
     [RaisesException] void arc(float x, float y, float radius, float startAngle, float endAngle, [Default=Undefined] optional boolean anticlockwise);
     [RaisesException] void ellipse(float x, float y, float radiusX, float radiusY, float rotation, float startAngle, float endAngle, [Default=Undefined] optional boolean anticlockwise);
 
     // FIXME: Simplify these using optional CanvasWindingRule once crbug.com/339000 gets fixed.
     void fill();
-    [RuntimeEnabled=ExperimentalCanvasFeatures] void fill(Path path);
+    [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] void fill(Path? path);
     void fill(CanvasWindingRule winding);
-    [RuntimeEnabled=ExperimentalCanvasFeatures] void fill(Path path, CanvasWindingRule winding);
+    [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] void fill(Path? path, CanvasWindingRule winding);
     void stroke();
-    [RuntimeEnabled=ExperimentalCanvasFeatures] void stroke(Path path);
+    [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] void stroke(Path? path);
     // FIXME: Simplify these using optional CanvasWindingRule once crbug.com/339000 gets fixed.
     void clip();
-    [RuntimeEnabled=ExperimentalCanvasFeatures] void clip(Path path);
+    [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] void clip(Path? path);
     void clip(CanvasWindingRule winding);
-    [RuntimeEnabled=ExperimentalCanvasFeatures] void clip(Path path, CanvasWindingRule winding);
+    [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] void clip(Path? path, CanvasWindingRule winding);
     boolean isPointInPath(float x, float y, optional CanvasWindingRule winding);
     boolean isPointInStroke(float x, float y);
 
     // text
     attribute DOMString font;
     attribute DOMString textAlign;
     attribute DOMString textBaseline;
 
     TextMetrics measureText(DOMString text);
 
@@ skipping 71 matching lines @@
     [RuntimeEnabled=ExperimentalCanvasFeatures] boolean drawCustomFocusRing(Element element);
 
     readonly attribute float webkitBackingStorePixelRatio;
 
     [ImplementedAs=imageSmoothingEnabled, MeasureAs=PrefixedImageSmoothingEnabled] attribute boolean webkitImageSmoothingEnabled;
     [MeasureAs=UnprefixedImageSmoothingEnabled] attribute boolean imageSmoothingEnabled;
 
     Canvas2DContextAttributes getContextAttributes();
 };