Implement basic parts of hit regions on canvas2d.

Source/core/html/canvas/CanvasRenderingContext2D.idl

Index: Source/core/html/canvas/CanvasRenderingContext2D.idl
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.idl b/Source/core/html/canvas/CanvasRenderingContext2D.idl
index 1738af041a40c2c63764caafc7e6ef3db267e018..e2cd13c828880eaef9d572a2fc31e74548be63df 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.idl
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.idl
@@ -123,6 +123,13 @@ enum CanvasFillRule { "nonzero", "evenodd" };
     [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] void drawImage(ImageBitmap imageBitmap, unrestricted float x, unrestricted float y, unrestricted float width, unrestricted float height);
     [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] void drawImage(ImageBitmap imageBitmap, unrestricted float sx, unrestricted float sy, unrestricted float sw, unrestricted float sh, unrestricted float dx, unrestricted float dy, unrestricted float dw, unrestricted float dh);
 
+    // hit regions
+    // FIXME: Blink does not currently support WebIDL dictionary definitions.
+    // See http://crbug.com/321462
+    [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] void addHitRegion(optional Dictionary options);
+    [RuntimeEnabled=ExperimentalCanvasFeatures] void removeHitRegion(DOMString id);
+    [RuntimeEnabled=ExperimentalCanvasFeatures] void clearHitRegions();
+
     // pixel manipulation
     ImageData createImageData(ImageData imagedata);
     [RaisesException] ImageData createImageData(float sw, float sh);