Add path option(path2d) for hit regions on canvas2d.

Source/core/html/canvas/CanvasRenderingContext2D.cpp

Index: Source/core/html/canvas/CanvasRenderingContext2D.cpp
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.cpp b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
index f06b7c6a5c8343a301221eb517d696ba5e7d3e84..a34a5332a8c1b1092859479e47387d46e7d98de7 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -2373,16 +2373,19 @@ void CanvasRenderingContext2D::addHitRegion(const Dictionary& options, Exception
         return;
     }
 
+    RefPtr<Path2D> path2d;
+    options.getWithUndefinedOrNullCheck("path", path2d);
+    Path specifiedPath = path2d ? path2d->path() : m_path;

[Justin Novosad, 2014/07/04 15:02:44]

specififiedPath is not necessarily a "specified path" since it can be m_path. 
Perhaps you should call it just "path" or "hitRegionPath".

[zino, 2014/07/05 03:01:22]

Done.

+
     FloatRect clipBounds;
     GraphicsContext* context = drawingContext();
 
-    if (m_path.isEmpty() || !context || !state().m_invertibleCTM
+    if (specifiedPath.isEmpty() || !context || !state().m_invertibleCTM
         || !context->getTransformedClipBounds(&clipBounds)) {
         exceptionState.throwDOMException(NotSupportedError, "The specified path has no pixels.");
         return;
     }
 
-    Path specifiedPath = m_path;
     specifiedPath.transform(state().m_transform);
 
     if (context->isClipMode()) {